Trichogramma ostriniae Pang and Chen (Hymenoptera: Trichogrammatidae) was reared continuously for seven generations on its native host, the Asian corn borer, Ostrinia furnacalis (Guenée) (Lepidoptera: Crambidae). It took 6.7 d at 33°C and 20 d at 17°C from oviposition to adult emergence with no differences between sexes. Several theoretic models were used to fit the temperature-dependent growth curves of T. ostriniae. A transformed day-degree model and the Hilbert-Logan model were the most reliable for predicting temperature development of T. ostriniae. The wasps reared on O. furnacalis at 27°C by the seventh generation had a lower level of parasitism than wasps from other generations and at other temperatures (17–33°C). The number of wasps emerged from individual parasitized egg, and percentage of females produced did not differ for any generations and temperatures. The differences among different generations for the amount and proportion of time female wasp spent drumming host eggs did not show any host- and generation-related trends. The time spent drumming by T. ostriniae female wasps reared for three generations on O. furnacalis and then four and six generations on the rice moth, Corcyra cephalonica (Stainton), differed slightly from the other generations. High variability among the tested wasps indicated that a large number of replicates would be needed to detect the probable differences among generations.

We tested the effects of different soils (soils A–F) representing four soil types, two moisture extremes (wet and dry), and two soil densities (packed and tilled) on the number of emerging Aethina tumida Murray (Coleoptera: Nitidulidae) adults. We further determined the effect of soil type and A. tumida sex on the time spent in the soil (where the beetle pupates). Three thousand A. tumida larvae were placed in the moist soil treatments (wet/packed and wet/tilled), of which 2,746 emerged from the soil as adults. Additionally, 3,000 larvae were placed in the dry soil treatments (dry/packed and dry/tilled), of which none emerged as adults. In only one soil were emersion rates different from those in other soils. For every soil, there were significantly more emerging A. tumida in the wet treatments than in the dry ones. Female A. tumida spent less time in the soil than male A. tumida but only by an average of less than half a day. Soil type did affect the length of time A. tumida spent as pupae, despite which average emersion as adults occurred within a tight range. The data suggest that biological requirements of A. tumida may limit/enhance their reproductive potential in various soil environments (especially in dry climates).

This study investigated the physiologically adaptive significance of elytral coloring and other thermal adaptations to different climes of Central and Northern Europe in a leaf beetle. Adults of Chrysomela lapponica L. differ in the coloring pattern of their red and black elytra when comparing populations from Finnish Lapland (Northern Europe) and from the Czech Republic (Central Europe). While the elytra of adults of the Czech population were bright red in color with a proportion of 51% of black marks, the relative size of the black marks of the Finnish beetle’s elytra was significantly higher (68%). When exposed to light, the dark morphs from Finland increased their body temperature within a shorter time and reached higher mean body temperatures than the lighter morphs from the Czech Republic. The walking speeds of the two different morphs did not differ at temperatures of 20, 15, and 10°C. However, at 5°C, the walking speed of the melanic beetles from Finland was significantly higher. The specific metabolic rate during overwintering of the adults was significantly higher in the Finnish morph at a temperature of 5°C compared with the Czech morph. The average and maximum temperatures during overwintering in the leaf litter layer in the Czech Republic were more variable and on average higher than under the snow cover in Finland. These results on the thermoregulation in C. lapponica are discussed with special respect to melanic elytral coloring as adaptation toward lower ambient temperatures.

Life history of immature Angoumois grain moths, Sitotroga cerealella (Olivier), was studied on dent corn (Pioneer 3320) at 10, 15, 20, 25, 30, 35, and 40°C and at 43, 53–61, 75–76, and 82–87% RH under laboratory conditions. At 10 and 40°C, none of the stages survived at any relative humidity. Temperature was the main factor affecting egg incubation period, larval-pupal development time, and egg and larval-pupal survivorship. The shortest egg development times occurred at temperatures of 30°C and higher, but they increased sharply as temperature decreased. Larval-pupal development time was shortest at 30°C. Survivorship was optimal at 20–30°C for eggs and larvae-pupae, but larval-pupal survivorship decreased sharply at 15 and 35°C. Duration of larval-pupal development did not vary with sex. Newly emerged females were twofold heavier than males, and temperature and relative humidity did not affect weight. Sex ratio of emerging adults did not differ from 1:1 at any temperature or relative humidity. The optimum conditions for development of Angoumois grain moth on corn were 30°C and 75% RH. The data will be useful for determining safe storage conditions for corn and for developing a computer model for simulating population dynamics of immature S. cerealella.

A classical biological control agent, Harmonia axyridis (Pallas), is having both beneficial and detrimental impacts in North America. The objective of this study was to evaluate the cold hardiness of H. axyridis in North America. Supercooling points and survival at subzero temperatures of field-collected and insectary-reared H. axyridis were examined. The mean (±SE) supercooling points for eggs and pupae (i.e., nonfeeding stages) were −27.0 ± 0.18°C and −21.3 ± 0.52°C, respectively. The mean supercooling points for larvae and adults (i.e., feeding stages) were −14.17 ± 0.33 and −11.9 ± 0.53°C, respectively. Sex and color morph (i.e., red: f. succinea versus black: f. spectabilis) had no effect on the supercooling point of H. axyridis adults. Mean supercooling points of H. axyridis adults from Minnesota and Georgia were significantly lower during winter months than summer months. The mortality of H. axyridis increased significantly after individuals were exposed to temperatures below the mean supercooling point of the population. Supercooling point was a good predictor of cold hardiness. However, the cold hardiness of H. axyridis appears to be a poor predictor of its northern distribution.

The effect of cold storage at 0.5, 5, 10 and 13°C on the developmental rates and survival of the pteromalid parasitoids Muscidifurax raptor Girault & Sanders, Muscidifurax zaraptor Kogan & Legner, and Trichomalopsis sarcophagae Gahan was examined in the laboratory. Immature M. raptor underwent development at 13°C, but not at 10, 5, or 0.5°C. Immature M. zaraptor and T. sarcophagae did not develop at temperatures ranging from 0.5 to 13°C. Parasitoid survival varied among storage temperatures and was lowest at 0.5°C for M. raptor and M. zaraptor and highest at 10°C. Survival of T. sarcophagae was highest at 5°C and was higher than either species of Muscidifurax at temperatures ≤5°C. M. raptor had the highest survival at 10 and 13°C. A simple model was used to examine the effects of cold storage and stockpiling parasitoids for up to three generations on parasitoid availability. Storage of M. raptor at 10°C for three generations could result in a 3.5-fold increase in availability. Storage of M. zaraptor at 10°C could result in a 2.6-fold increase in availability, and storage of T. sarcophagae at 5°C could result in a 3.2-fold increase in availability. Results suggest that cold storage could be a useful method for increasing the rearing efficiency of these parasitoids.

The multicolored Asian lady beetle, Harmonia axyridis (Pallas), is displacing native coccinellid species in North America. To elucidate the mechanisms underlying this phenomenon, it is important to understand its physiological ecology. Hence, this study examined the temperature dependence of the respiratory physiology of this species. Calorespirometry was used to measure metabolic heat and CO₂ production rates from second, third, and fourth instars; pupae; and adult beetles at temperatures from 0 to 40°C at 5°C intervals. Mass-specific respiration rates, in terms of either CO₂ or heat production, increased with temperature, and, with the exception of pupae, decreased with increasing development. For all developmental stages, the results showed that below 10°C, CO₂ was produced primarily from nonoxygen-consuming reactions. CO₂ production gradually shifts more to oxygen-consuming reactions with increasing temperature, the fraction of CO₂ from oxygen-consuming reactions reaching 0.5–0.7 at 40°C. Adults and second instars were stressed at 35°C and showed high mortality at 40°C, but these conditions were tolerated by all other stages studied. These data agree with field observations of the success of the multicolored Asian lady beetle in the temperature range from 15 to 25°C.

Delphastus catalinae (Horn) is a predator of whiteflies that has shown promise as a tool in pest management strategies. Exposure to short-term temperature extremes can affect the survival of predators in a greenhouse or field environment. The B-biotype sweetpotato whitefly, Bemisia tabaci (Gennadius), survives the winters of mild climates (where temperatures are commonly above 0°C), but it is not known if D. catalinae can survive such winters. The influence of constant temperature on the survival of D. catalinae was determined in the laboratory using eggs and nymphs of the B-biotype B. tabaci. Over 90% of the adult beetles exposed to temperature regimens of 5, 10, 15, 20, 25, 30, and 35°C for 24 h survived when confined with hosts. The lower and upper thresholds for survival over that duration were around 0 and 40°C, respectively; ∼1% of the insects survived temperatures beyond these extremes. Survival of D. catalinae pupae was similar to that of adults. Adult D. catalinae survived up to 5.8 mo when confined on a plant infested with whitefly eggs and nymphs and held at 25°C; 50% of the cohort survived for 3.4 mo. Those held in a similar test at 35°C lived up to 0.6 mo. The number of immature whiteflies consumed during 24 h by adult D. catalinae generally increased with temperatures of 14–30°C. This study provides information on temperatures that may affect the survival of D. catalinae during commercial shipment and after release for biological control in the field or greenhouse, and it may help in the understanding of their ability to survive mild winters.

Cortical and sapwood volatiles were collected in situ from red spruce, Picea rubens (Sarg.), trees infested with Tetropium fuscum (F.), to determine the relative concentrations and enantiomer ratios of monoterpenes emitted. This information was used to create a synthetic “spruce blend” lure that was tested in various trap designs for efficacy in capturing T. fuscum, and Tetropium castaneum L. in field bioassays conducted on McNabs Island, Nova Scotia, in 2001 and 2002 and in Poland and Switzerland in 2002. Response of other cerambycid species was measured opportunistically. Cross-vane pan traps baited with spruce blend caught significantly more T. fuscum than unbaited traps or traps baited with racemic α-pinene, ethanol, or both. The addition of an ethanol lure to spruce blend–baited traps significantly increased capture of T. fuscum and T. castaneum. There were no significant differences among trap designs in mean catch of either Tetropium species. Spruce blend was also significantly attractive to Monochamus urussovii (Fischer) and, when paired with an ethanol lure, was significantly attractive to Spondylis buprestoides L. Asemum striatum L. was significantly attracted to racemic α-pinene but was not attracted to spruce blend or spruce blend plus ethanol. None of the lures tested were significantly attractive to Stictoleptura rubra L. or Alosterna tabacicolor (DeGeer).

Gregarious and quasi-gregarious parasitoid females can either mate on the emergence patch or disperse and mate later. The temporal pattern of dispersion of males and females and the level of predispersal mating for females were measured in three egg parasitoid species: Trichogramma evanescens Westwood, Trichogramma minutum Riley, and Trichogramma pintoi Voegele (Hymenoptera: Trichogrammatidae). Results showed that T. minutum has a higher proportion of virgin females in the dispersing population than T. pintoi and T. evanescens. However, the fact that a proportion of dispersing virgin females was found in all three species indicates some level of genetic exchanges between subpopulations of these egg parasitoids. Results suggest that all species can show partial local mating at different levels.

Western corn rootworms, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), with resistance to crop rotation, frequently move between fields of corn, Zea mays L., and soybean, Glycine max L. Merril, laying eggs in both crops. By comparing the behavioral and reproductive responses of beetles experiencing mixed corn and soybean diets to those provided with a continuous corn diet, the cost of mixing diets was measured. Larvae were collected near Urbana, IL (rotation-resistant population), and Monmouth, IL (typical rotation-susceptible population), and reared to adults in the laboratory. Females from each population were assigned to alternating corn and soybean diets of different durations. Beetles were more likely to feed on corn if it followed soybean than if they had continuous access to corn. The cost of a mixed corn and soybean diet was minimal; the fecundity of females given alternating diets of corn and soybean was similar to that of beetles given daily access to corn diets. Females laid more eggs on days when they had access to soybean than on days with access to corn, suggesting dietary stress can induce oviposition. The only behavioral difference between the populations was a greater sensitivity to daily alternation of corn and soybean diets among beetles from the rotation-susceptible population. We found no evidence that rotation-resistant adult D. v. virgifera have any greater inclination or capacity to feed on soybean tissue than rotation-susceptible adults. Instead, periodic exposure to soybean results in nutritional stress that increases oviposition rate, lowers the threshold for feeding, and increases beetle activity.

The milfoil weevil, Euhrychiopsis lecontei Dietz, is a North American herbivore associated with declines of Eurasian watermilfoil (Myriophyllum spicatum L.) in the United States. The weevil is a watermilfoil specialist and northern watermilfoil (M. sibiricum Komorov) is its native host plant. Previous studies have reported better developmental performance (egg to adult development) on Eurasian watermilfoil (exotic host) than on northern watermilfoil (native host). The reported difference in performance between host plants and the weevil’s occurrence in two distinct geographical regions in Washington State (eastern and western Washington) led us to conduct laboratory experiments to compare the developmental performance between weevil and host plant populations. No significant differences were detected in the egg to adult development time for eastern and western Washington weevils reared on Eurasian or northern watermilfoil from both regions. Regional differences, however, were found in egg to pupa development time, number of days spent as a larva, and body size at emergence. Eastern Washington weevils (northern watermilfoil source population) reared on northern watermilfoil from western Washington had significantly longer egg to pupa development time and larval stage than weevils reared on northern watermilfoil from eastern Washington. In addition, eastern Washington weevils reared on northern watermilfoil from eastern Washington had significantly greater body length than those reared on Eurasian watermilfoil from western Washington. Results indicate that developmental performance on Eurasian watermilfoil is not always better than on northern watermilfoil, and performance may vary with watermilfoil population and/or host plant quality.

Male fall armyworm moths [Spodoptera frugiperda (J. E. Smith)] were captured in pheromone traps over a 16- to 24-mo period in selected sites in southern Florida. Molecular markers were used to determine whether individuals were of one of two host strains (historically designated “rice-strain” and “corn-strain”). Traps placed in agricultural areas showed a population peak in the spring (March–May) and fall (October–December), with a prolonged decline in numbers in summer (July–October) and a smaller reduction in mid-winter (January). The host strain distribution during these periods varied significantly, suggesting strain-specific and seasonal population patterns. Both strains were captured in substantial numbers during the spring peak, but surprisingly, only the rice-strain showed an increase in capture rates during the fall, despite the presence of sweet corn throughout this period. Trap captures in a sod (turfgrass) farm were composed almost entirely of the rice-strain and showed a bimodal seasonal distribution similar to that seen in the agricultural areas, with peaks in the spring and fall. These results represent the first indication that the two host strains might have substantially different population dynamics in the overwintering agricultural areas of Florida and suggest that the rice-strain is the predominant fall armyworm pest during the fall and winter growing periods. It further indicates that the two strains can display a markedly different response to seasonal environmental cues. The implications of these findings on our understanding of fall armyworm migration are discussed.

We describe the dynamics of potato leafhopper, Empoasca fabae (Harris) (Homoptera: Cicadellidae), populations in a 4-ha alfalfa field over 2 yr. Population growth and spatial structure were strongly influenced by days after cutting. Capture of E. fabae by suction traps above the boundary layer along with sex ratios of in-field populations suggested that immigrants contributed to population growth throughout the second and third alfalfa growth cycles. Initial sex ratios were strongly female biased (1995, 80%; 1996, 90%), with the degree of bias decreasing and approaching a 1:1 ratio through the third growth cycles. A higher proportion of the population was located in the edge relative to the interior plots in three of four alfalfa growth cycles. Spatial correlation between females and males was initially low, but increased as density increased; this correlation also decreased immediately after alfalfa harvest, and significantly increased over time after harvest. These data suggest that dynamic in-field spatial organization exists for E. fabae. Although the entire field was colonized, we hypothesize an edge-biased colonization process, initiated by females for at least the second growth cycle in the northeastern United States, followed by density-dependent movement away from crowded areas of declining host quality.

The habitat associations of Ixodes scapularis Say (=I. dammini Spielman, Clifford, Piesman, and Corwin) were examined at the northern edge of its range. We assessed the association of habitat features with the abundance of ticks by flagging for questing adult I. scapularis at three sites in coastal Maine from 1998 to 2000 along 27 305-m transects. Multivariable logistic regression indicated that probability of tick abundance was greater in the presence of shrub layer, canopy closure >50%, deciduous litter, forest grasses, and moist-soil ferns. In a second model that related I. scapularis abundance to canopy- and shrub-layer species, probability of tick abundance was greater in the presence of Japanese barberry Berberis thunbergii DC, winterberry holly Ilex verticillata L. (Gray), and Eurasian honeysuckle Lonicera spp., and less with the presence of eastern hemlock saplings Tsuga canadensis L. (Carr.). These associations were true despite variation in deer abundance as indicated by deer pellet group counts. Natural resource managers should be aware that landscape changes, including the invasion by exotic vegetation, might create favorable tick habitat. These findings could prove helpful in assessing local risk of exposure to this vector tick.

This investigation is the first to quantify the degree of habitat specialization for any species within the little-known order Embiidina. The lichen and plant communities found in the habitats of two sympatric species, one living on lichens encrusted on granite and another feeding in leaf litter, were characterized using a process of ordination and cluster analysis. Differences among 40 samples and their relationships to environmental factors were probed statistically using Spearman’s coefficient of rank correlations generated by comparing rank similarity matrices of the census sites. The lichen eater, Notoligotoma hardyi (Friederichs), was more abundant in areas with strong southern exposures and was associated with higher lichen abundance. They preferentially grazed on particular lichens, the first indication that an embiid shows specialization in feeding. The detritivore, Australembia incompta Ross, was closely associated with particular plant communities, especially those less susceptible to fire. Their colonies were more common in rockier, coastal areas and less abundant in grasslands and habitats dominated by Eucalyptus. Insight into ecological variation within the order can guide further exploration of other traits (such as silk structure and function and primitive social behavior) in this rarely studied group of insects.

The widespread planting of crops genetically modified to produce Bacillus thuringeinsis Berliner (Bt) toxins for pest control may affect nontarget arthropods. To address this issue, we compared the abundance and diversity of arthropods on plants in field plots of Bt cotton, non-Bt cotton, and a row mixture of 75% Bt cotton and 25% non-Bt cotton at two sites in Arizona. Over three sampling dates during 2 yr, we recorded all of the arthropods found on 120 cotton plants per treatment. This yielded 3,309 individual arthropods from 69 families. Excluding pink bollworm, Pectinophora gossypiella Saunders, the pest targeted by Bt cotton, we compared the abundance and diversity of all arthropods, chewing herbivores, sucking herbivores, rasping-sucking arthropods, and natural enemies. Arthropod abundance was significantly affected by site, plant height, and cotton type. More arthropods were collected from row mixture plots than Bt plots, but arthropod abundance did not differ significantly between Bt plots and non-Bt plots. The number of families collected was 57 for row mixture plots, 55 for non-Bt plots, and 47 for Bt plots. The number of families increased as arthropod abundance increased, suggesting that the differences in diversity among treatments were caused by differences in abundance. Within row mixture plots, arthropod abundance and diversity did not differ significantly between Bt plants and non-Bt plants. We conclude that the differences between Bt and non-Bt cultivars had relatively minor effects on the arthropod community on cotton plants.

Experiments were undertaken to determine the potential for using rubidium chloride (RbCl) or cesium chloride (CsCl) to mark southwestern corn borer, Diatraea grandiosella Dyar, for use in applied ecological studies. Maize, Zea mays L., plants were sprayed with aqueous solutions of RbCl or CsCl at rates of 100, 1000, or 10,000 μg/g and inoculated with D. grandiosella neonates. Rubidium and cesium were successfully absorbed and translocated in maize plants. There were only a few minor effects of the treatment on maize or on southwestern corn borers. Rb and Cs were detected in plants, but not in insects, by using flame atomic absorption spectrophotometry. Graphite furnace-atomic absorption spectrophotometry (GF-AAS) and neutron activation analysis (NAA) allowed identification of Rb and Cs in adults. Rb and Cs were detected by GF-AAS in feral unmarked adults, and they contained higher levels of Rb than Cs. Males and females contained similar amounts of Rb, but Cs levels were higher in males than in females. Adults recovered from field maize treated with 1000 μg/g Cs had higher levels of Cs than did those from untreated plants. Using NAA, neither Rb nor Cs was detected in adults recovered from greenhouse-grown untreated maize. Males and females recovered from maize treated with 1000 μg/g RbCl and CsCl contained similar amounts of Rb, but females contained more Rb than Cs. We conclude that application of 1000 μg/g RbCl or CsCl on plants is effective in marking adults of D. grandiosella with Rb or Cs and would be useful for mark–recapture dispersal studies.

A method is described for estimating the impact of a parasitoid on the abundance of a nontarget host, using the intrinsic rate of host increase, the average abundance of the host in the presence of parasitism, and the estimated mortality caused by the parasitoid. The method is applied to the braconid Microctonus aethiopoides Loan, introduced to New Zealand to control Sitona discoideus Gyllenhal in lucerne but also attacking native weevils Irenimus spp. and Nicaeana spp. The nontarget host population was modeled using discrete Ricker or continuous logistic models, tuning the models to host population data in the presence of parasitism, then removing parasitism and determining the increase in predicted equilibrium host density. In an area where up to 30% parasitism of a nontarget host population has been recorded, the model estimated an 8% reduction of the nontarget host. In another area, where the parasitoid has not established, the method was applied in reverse to predict the parasitoid’s impact if it did establish. In this case, the model predicted a 30% suppression of population density. The host’s intrinsic rate of increase, r_m, accounts for this difference in predicted impact, which was small in the low altitude area where r_m was high, and the impact was larger in the higher altitude site where r_m was smaller.

Interactions between the solitary endoparasitoid Meteorus gyrator (Thunberg) and the pathogen Lacanobia oleracea (L.) granulovirus (LoGV) were investigated in the host L. oleracea. The ability of M. gyrator to develop within an LoGV-treated host was dependent on the time of parasitism relative to the time of infection. The likelihood of survival of the parasitoid increased as the time between oviposition of the parasitoid egg and ingestion of the virus by the host increased. LoGV-induced death of the host resulted in death of the developing parasitoid. No parasitoids emerged from hosts that were infected with LoGV before parasitoid oviposition. Host treatment with LoGV after parasitization had occurred had no pronounced effects on parasitoid larval or pupal developmental times or on the weight of the parasitoids’ cocoon after egression from the host. There were also no indications of direct infection or toxic effects of LoGV on the developing parasitoid larva. Adult M. gyrator were able to discriminate between healthy and LoGV-treated hosts. Hosts treated with LoGV were parasitized less frequently than untreated hosts, and fewer eggs were laid in LoGV-treated hosts. Transmission of virus from infected to healthy hosts via contamination of the wasp was low (1.5%). Percentage mortality of the host was significantly higher when a combination of the two biological control agents was used compared with either the virus or the parasitoid on its own. The practical use of these two agents was demonstrated in a glasshouse trial that confirmed that damage to tomato plants by L. oleracea larvae could be reduced using LoGV or parasitoid treatment. Although damage was further reduced by using a combination of the two agents, this was not significantly lower than that for LoGV treatment alone.

We monitored numbers of Coleomegilla maculata DeGeer and Harmonia axyridis (Pallas) eggs, larvae, and adults in an Illinois cornfield during anthesis. Larvae and adults were collected from the field and their gut contents were examined. Also, daily pollen deposition was recorded over the sample period, and prey biomass per plant was calculated for each of four replicate plots of field corn. The numbers of egg clutches and adults per plant were compared with daily pollen deposition, and pre- and postanthesis daily pollen deposition, densities of egg clutches, and adult densities were compared. Also, we compared the numbers of larvae and adults collected per plot and pollen and prey densities in the plots. Finally, the proportions of larvae and adults that had fed on corn pollen or prey were compared between predator species. We found that the number of coccinellid egg clutches increased significantly after anthesis and that the densities of adults of both species were not significantly different pre- and postanthesis. Larval and adult populations of H. axyridis were significantly correlated with prey densities, but C. maculata were not. All instars of C. maculata and H. axyridis occurred in corn during anthesis, and corn pollen was found in the guts of all four instars and in adults of both species. Dissections revealed that the majority of C. maculata larvae and adults had pollen in their guts, and a minority of H. axyridis larvae and a single adult had pollen in their guts. Conversely, the majority of H. axyridis larvae and adults had insect prey in their guts, and <40% of C. maculata larvae and adults had prey in their guts. Potential mechanisms for the numerical increases of coccinellids observed during anthesis and the implications of pollen feeding for risk assessment of transgenic insecticidal corn to C. maculata are discussed.

The predator Geocoris floridanus Blatchley has become more common in row crop systems in Georgia, but its ecology is unknown. We studied selected life-history characteristics of G. floridanus in the laboratory. Two prey treatments were evaluated for nymphs and adults of G. floridanus: 1) eggs of the corn earworm, Helicoverpa zea (Boddie), and (2) young larvae of the beet armyworm, Spodoptera exigua (Hübner). G. floridanus nymphs were reared on the prey, and predator development and prey consumption were monitored; predation rates, longevity, and fecundity of adults were evaluated. Nymphal development times and number of prey consumed by predators fed corn earworm eggs were similar for females and males. Nymphal development of predators fed beet armyworm larvae was prolonged compared with predators reared on corn earworm eggs. Nymphal survival was unaffected by prey type. Nymphs reared on corn earworm eggs required fewer prey to complete nymphal development and produced larger adults. Females fed corn earworm eggs had shorter preoviposition periods, and greater fecundity and longevity than females fed beet armyworms. Females consumed more beet armyworms than corn earworm eggs, but produced fewer eggs per unit prey. Female predators fed beet armyworms while nymphs and switched to corn earworm eggs when adult partially recovered their fecundity, and exhibited life-history characteristics equal to those of females fed corn earworm eggs throughout their lives. Thus, G. floridanus can feed, develop, and reproduce on both prey species, and its performance increases when switched from beet armyworm larvae to corn earworm eggs.

Microbial control of red imported fire ant, Solenopsis invicta Buren, by the entomopathogenic fungus, Beauveria bassiana (Balsamo) Vuillemin, has been inconsistent. Therefore, fungal isolates and precisely controlled soil moisture and composition were investigated as possible limiting factors. For each experiment, ant colonies were collected from the field and placed into 19-liter buckets at room temperature. Fungal inoculation in all experiments was by point-source placement of B. bassiana growing in a single 100 by 15 mm petri dish into the colony; data were collected for 8–10 wk on percentage infection and on ant numbers by a stake-count method and by a population-index rating. Two fungal isolates did not differ in efficacy, and both were inferior to GardStar (permethrin) in killing the ants. B. bassiana reduced ant numbers more effectively in −0.2 bar soil than in −0.5 bar soil, which in turn was better than 0 bar (wet) or −1.0 bar (dry) soil moisture. Even in dry soil (−1.0 bar), however, up to 22.5% of the ants were infected. According to all three parameters, B. bassiana killed more ants in silt (70:15:15, silt:sand:clay) and in sandy soil (15:70:15) than in clay (15:15:70). Results with B. bassiana in clay did not differ significantly from the control.

The activity of the nucleopolyhedrovirus of the fall armyworm, Spodoptera frugiperda (J. E. Smith) (SfMNPV), on transgenic sweet corn, Zea mays (L.), expressing a CryIA(b) toxin from Bacillus thuringiensis (Berliner), was studied in the laboratory. As the line of Bt corn that we studied has only limited efficacy against the fall armyworm, SfMNPV was evaluated as a supplemental treatment. When fall armyworm larvae reared on transgenic or nontransgenic foliage were fed equal dosages of occlusion bodies (OB), measured either as OB per larva or as OB/mg larval weight, mortality was higher among larvae feeding on transgenic corn. However, when larvae were allowed to feed ad libitum on treated foliage, mortality was higher in larvae on the nontransgenic corn. Rates of food consumption were higher on nontransgenic corn, apparently resulting in ingestion of more OBs and countering increased susceptibility of larvae on transgenic corn.

Feeding and oviposition on different parts of mile-a-minute weed, Polygonum perfoliatum L. (Polygonales: Polygonaceae), by Rhinoncomimus latipes Korotyaev (Coleoptera: Curculionidae), a potential biological control agent for the weed, were studied in quarantine. An additional experiment was conducted to test the effects of different levels of simulated damage by R. latipes on P. perfoliatum growth, survival, and reproduction. Female weevils consumed more P. perfoliatum overall than males and selectively fed on capitula more than on ocreae or leaves, whereas males fed more on ocreae than on leaves or capitula. More eggs were also laid on capitula than on other plant parts. Female feeding preference is probably because of the high protein content of the capitula, because protein is required for continued egg production, whereas males may maximize their reproductive success by feeding low and close to P. perfoliatum stems to intercept females as they emerge from pupation in the soil and ascend the plants to feed. The feeding and oviposition preferences of female R. latipes for plant capitula suggest that host specificity tests for this species should be conducted with plants that are flowering. Damage that simulated the effect of R. latipes larval feeding caused plant mortality when it was initiated on small P. perfoliatum plants and reduced biomass and seed production when it was initiated on larger plants. Thus R. latipes could have a substantial impact on P. perfoliatum if the weevil is released into the weed’s introduced range in North America.

A prerelease assessment of impact by a potential biological control agent, Floracarus perrepae Knihinicki and Boczek, on the invasive weed, Lygodium microphyllum (Cav.) R. Br., was conducted in a 2-yr field study in their native range—Australia. Thirty-two pairs of test plants were planted in a field plot with two levels of shade, with one plant in each pair treated biweekly with the miticide abamectin. The mite caused a significant reduction in biomass of above ground stems and leaves and below ground roots and rhizomes. The mean leaf longevity was significantly longer for the treated versus the mite infested untreated plants. Populations of native predator mites were low throughout the study; however, the mite pathogen Hirsutella thompsonii Fisher was common in the second year of the study, but neither reduced the impact of F. perrepae. Based on its potential to cause significant damage to L. microphyllum under field conditions in the native range and extremely narrow field host range, F. perrepae is an excellent candidate for biological control of this invasive fern in Florida.

Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae) is the most prevalent insect species in granaries in western Canada. Their movement and distribution at different environmental conditions provide important information for insect detection and control and for models of their distribution in grain bins. The distribution and wandering movement of C. ferrugineus adults were studied in a 100 by 500 by 500-mm wheat (14.5 ± 0.2% moisture content) chamber with or without a 5°C/m temperature gradient. In the grain chamber at a uniform temperature, adults dispersed homogeneously in each horizontal layer and heterogeneously in the vertical direction when the temperature was 22.5–30°C. Adults moved toward a warmer temperature and in the direction of gravity at the same time in the grain chamber with temperature gradients in the horizontal or/and vertical directions. Adult movement and distribution in the two-dimensional chamber could be represented by published data obtained in one-dimensional columns. The movement and distribution of females (mixed ages) were not significantly different from those of males (mixed ages) in response to temperature gradients and gravity. Wandering movement of adults was restricted by temperature gradients.

Laboratory assays were performed to determine the impact of three predators, the bigeyed bug, Geocoris punctipes Say, minute pirate bug, Orius insidiosus (Say), and the pink spotted lady beetle, Coleomegilla maculata fuscilabris (Mulsant), on two herbivores, the cotton aphid, Aphis gossypii Glover, and the twospotted spider mite (TSM), Tetranychus urticae Koch, using strawberry (Fragaria ananassa Duchesne) leaflets as a substrate. Both herbivores are considered important strawberry pests worldwide. Daily and hourly consumption of a single prey species studied were conducted as well as a preference for prey test. All stages of the bigeyed bug, minute pirate bug, and pink spotted lady beetle fed on the cotton aphid and TSM. The pink spotted lady beetle had a higher rate of consumption for both the cotton aphid and TSM, and therefore, may be a more effective predator of both prey species. The bigeyed bug and minute pirate bug (third instar and adult) prefer TSM over cotton aphids based on handling time. In contrast, the pink spotted lady beetle (third instar and adult) prefers aphids over mites. Results from these experiments indicated that the pink spotted lady beetle seems to be a good predator to incorporate into an existing biological control program for cotton aphid and TSM on strawberries. Better understanding of these three predators will lead to their more efficient use for biological control of aphids and TSM.

Lepidoptera feed at mud puddles, dung, and carrion in a behavior known as puddling. Sodium and sometimes protein are feeding cues, are actively collected, and play a potentially important role in lepidopteran nutritional and mating ecology. We showed that montane butterfly species have feeding preferences among mud, herbivore dung, and carnivore dung, and that these preferences differed among butterfly species. The puddling substrates varied in soluble sodium content, with mud having the lowest concentrations and carnivore dung having the highest. Within one species, Pieris napi L., visit frequencies to mud versus dung matched visit frequencies to sand trays filled with sodium solutions matching the concentrations seen in mud or dung. This suggests that the preference hierarchy of this species is driven by soluble sodium concentration. Overall, the results indicate that lepidopteran species specialize on different puddling substrates, likely obtaining different arrays of nutrients. This suggests that there are species- or family-specific roles for puddling nutrients in the overall nutrient budget of the insects.

In the past few years, a number of transgenic plants expressing Bacillus thuringiensis (Bt) proteins have been commercialized throughout the world, particularly in the developed countries. In developing countries, the process of commercializing insect-resistant transgenic crops has begun and is likely to gain momentum in the near future. Resource-poor farmers who are unable to afford the cost of genetically modified (GM) seed fear that the pests will avoid GM fields and instead attack their non-GM fields. A study was conducted in India to elucidate whether pests will avoid the transgenic Bt crop and congregate in the fields with non-GM crops. Transgenic Bt cabbage and nontransgenic cabbage were compared for their suitability for oviposition, larval feeding, and orientation by the diamondback moth, Plutella xylostella, in the laboratory. Data presented in this study show that adult P. xylostella were equally attracted to transgenic and nontransgenic cabbage plants. Larval attraction to both types of plants was also equally high. After hatching on the transgenic cabbage plants, first instar larvae suffered 100% mortality and, therefore, did not move to nearby nontransgenic plants. However, the larvae released on the nontransgenic plant were attracted to transgenic plant placed in its vicinity and suffered heavy mortality.

Exotic predators are sometimes introduced into agricultural ecosystems to aid in biological control of crop pests. Besides direct effects, such as consumption, introduced predators can have indirect effects on smaller predators and herbivores through chemically mediated shifts in behavior. We tested whether the chemical cues of Tenodera aridifolia sinensis (the Chinese praying mantis) affected the movement and foraging of the native wolf spider Pardosa milvina. Comparisons of behavior in paired-treatment arenas revealed that P. milvina spent a greater amount of time immobile, had a greater residence time, and moved at a significantly slower speed on T. a. sinensis cues relative to a blank control. While this reduced movement may reduce the probability of predation, it has a cost in terms of foraging. P. milvina gained less mass and had a smaller increase in abdomen width after foraging in microcosms containing T. sinensis cues relative to blank controls. The response of P. milvina to chemical cues of mantids is similar to the response of this small wolf spider to chemical cues from a larger, coexisting wolf spider predator. While these effects appear important in the lab, further studies are needed to evaluate the impact of cues on populations of P. milvina in the field.

The sunflower midge, Contarinia schulzi Gagné (Diptera: Cecidomyiidae), is a pest of cultivated sunflower (Helianthus annuus L.). Larval feeding can cause damage and yield loss to the sunflower head. Adult emergence is extended and larvae are well protected in the sunflower receptacle, making chemical control methods difficult and expensive. Sunflower midge enter sunflower fields at the edges but fieldwide distributions occur, although the dynamics are not fully understood. Two commercial fields in 1999 and one field in 2000 were systematically sampled by dividing each field into fixed sample points. Mean egg and larval densities from each sample point were used to describe sunflower midge populations. The sunflower heads at each sample point were also assessed for damage. Maps of sunflower midge population density, cumulative density, and sunflower head damage ratings were estimated with kriging interpolation. Maps were estimated several times during first generation sunflower midge infestation. Field edges that were initially populated continued to be areas of infestation throughout the sampling period. Damage ratings were related to population densities when infestations were high. In 2000, we tested the larval hatching rate from different-sized egg masses with regression to determine an estimation technique for combining numbers of eggs and larvae.

Airborne multispectral digital imagery was used to detect imported fire ant mounds in northeast Mississippi pasture. Images were acquired using a GeoVantage GeoScanner camera system, flown at an altitude of 610 m, for a resolution of 0.25 m, and 305 m, for a resolution of 0.1 m. Images were obtained during May 2002, August 2002, November 2002, and February 2003. Distinct mound signatures could be seen in images from May, November, and February; August images were difficult to interpret. Many mounds appeared as dark or light spots of bare soil surrounded by a halo of vigorous vegetation. Up to 75% of mounds were visible in false color infrared images. Mound characteristics (area, height, activity, percent vegetation cover) and image characteristics (image color, spatial resolution) all affected mound detection for at least one sampling period. Increasing spatial resolution from 0.25 to 0.1 m did not affect mound detection in May; during other times of the year, increased resolution improved detection by ≈38%. False color infrared images were generally superior to true color images for mound detection. Potential overestimation because of commission errors was 17–29%.

Two general hypotheses that describe the relationship between plant quality and host-plant preference of insect herbivores are the plant-stress and plant-vigor hypotheses. We examined the response of a gall-forming guild of insect herbivores associated with prairie rose, Rosa arkansana Porter (Rosaceae), to experimental manipulations of plant stress (addition of NaCl) and vigor (addition of nitrogen; NH₄NO₃). The most common members of the gall-forming guild on roses are Diplolepis ignota Osten Sacken, D. nodulosa Beutenmüller, and D. rosaefolii Cockerell (Hymenoptera: Cynipidae). The repeated application of nitrogen throughout the growing season to prairie plots resulted in significantly higher plant nitrogen levels and plant growth rates. Both low and high NaCl additions caused leaves to turn yellow and wilt, but reductions in rose growth rates or xylem water potentials with NaCl additions were not statistically significant. All three members of the cynipid guild responded similarly to nitrogen and NaCl additions to rose plots. Incidence of occurrence and density within a plot decreased with increasing nitrogen or NaCl, but the decline associated with increasing NaCl was not significant for any of the cynipids. Neither the plant-vigor hypothesis (higher abundance on fast-growing, vigorous plants) nor the plant-stress hypothesis (higher abundance on physiologically stressed plants) was supported by this study. For cynipids, there is growing evidence that larvae perform best on plant tissues low in nitrogen (less vigorous plants). Agricultural runoff, of which nitrogen is an important constituent, may be significantly altering cynipid distributions and their interactions with other members of the tall-grass prairie ecosystem.

Because plant nitrogen content varies within and between plants, insects must often compensate for low nitrogen levels by consuming more or suffer decreased performance. To test the effects of varying nitrogen content and plant characteristics that are affected by nitrogen content on monarch butterfly (Danaus plexippus L.) growth and development, we applied high and low nitrogen fertilizer treatments to common milkweed grown in a glasshouse. High nitrogen fertilization resulted in increased leaf nitrogen and plant height, but also higher disease and pest levels. Monarchs fed plants in the low nitrogen fertilization treatment showed higher relative consumption rates. Monarch performance, measured with development time and relative growth rate, was affected differently in different larval stadia, but larvae of all stadia fed leaves from the low nitrogen fertilization treatment weighed as much as or more than those fed high nitrogen leaves. These results suggest that monarch larvae compensate for lower plant quality by consuming more. If increased consumption is costly because of increased exposure to natural enemies or increased expenditure on consuming and processing food, low nitrogen host plants may result in decreased fitness, despite the monarchs’ ability to compensate.

High-intensity fires are known to kill adult and larval bark beetles, but it is unclear how mountain pine beetles (Dendroctonus ponderosae Hopkins) respond to trees that have been damaged by lower-intensity ground fires at the periphery of burns. We conducted an experiment to determine whether mountain pine beetles preferentially attack trees that have been damaged by fire and to determine how fire damage affects beetles’ reproductive success. We simulated different intensities of ground fires by artificially burning a strip of bark that extended zero-thirds, one-third, two-thirds, or three-thirds around a tree’s circumference. Burn treatments were applied ∼7 wk before beetles emerged from surrounding trees. We found that beetles did not preferentially attack fire-damaged trees; fire damage had no effect on the number of beetles landing on a tree, which trees were attacked, attack rate, attack density, or the body size of beetles attacking a tree. Beetle reproductive success (number and condition of offspring) was also not affected by fire damage. Beetles were more likely to overcome tree defenses and produce successful egg galleries on fire-damaged trees than on undamaged trees, but this was only observed on trees with low beetle attack densities. If beetle attack density was high, trees were successfully attacked irrespective of burn treatment. Our results suggest that fire damage only affects mountain pine beetle reproduction and population growth in areas where attack densities are low. In other situations, fire damage will have negligible effects on beetle attack and reproductive success.

Aphis fabae Scopoli consists of a complex of closely related host plant-associated forms. This system offers insights into speciation and the determinants of plant use in an important insect pest, but concerted study of the complex requires identification of clones with different plant preference that can potentially exchange genes. This study presents a series of hybridizations between clones collected from subspecies-specific host plants Vicia faba (L.), Tropaeolum majus (L.), and Cirsium arvense (L. Scopoli) that are carried out exclusively in the laboratory (mating and diapause) and also in the laboratory with overwintering in the field. Crosses between a V. faba-affiliated clone and T. majus and C. arvense-affiliated clones are not viable, but the cross between the T. majus and C. arvense-derived clones is highly viable and similar in fertility to the cross between the V. faba-derived clones with the same plant species preference (the “control”). It is also found that the female × male; cross between the T. majus and C. arvense-affiliated clones is viable when conducted exclusively in the laboratory but infertile in the laboratory/field crosses. This indicates that modifications of protocol can profoundly affect the outcome of aphid crossing studies and could explain the discrepancies between results of hybridization studies of the A. fabae complex carried out by various workers over the past 50 yr.

Induced plant responses to herbivores and pathogens have been found in many systems. We examined intra- and interspecific interactions among three parasites through induced responses in their shared host plant, papaya. Three key parasites attack papaya foliage in Hawaii: the carmine spider mite, Tetranychus cinnabarinus (Boisduval); the papaya rust mite, Calacarus flagelliseta Fletchmann, De Moraes, and Barbosa; and the powdery mildew causal agent, Oidium caricae F. Noack. Under laboratory conditions, papaya seedlings were first exposed to standardized populations of mites and mildew; the parasites were removed, and the clean, previously infested plants were transplanted into the field to be exposed to colonization by natural populations of plant parasites. Population growth of colonizers was monitored for a period of 3 mo. We found no evidence for induced plant resistance. Rather, our results suggest that papaya expresses a weak form of induced susceptibility after injury from papaya rust mites and powdery mildew. Plants exposed to rust mites as young seedlings subsequently supported larger populations of spider mites, and plants exposed early to powdery mildew subsequently supported larger populations of rust mites.

A field study examined the influence of southern green stink bug, Nezara viridula L., on late-season yield losses in cotton, Gossypium hirsutum L. These indirect harvest losses included rotted (complete tissue decay associated with pathogens) and hard-locked bolls (individual locules within a boll that remain compact and fail to open normally, associated with abiotic or biotic agents). Stink bugs were caged in plots of cotton under conditions of high rainfall and humidity, which favor pathogen development and physiological disorders in bolls. Boll-rotting pathogens (Diplodia spp. and Fusarium spp.) were isolated from rotted bolls. The percentage of rotted (2.0-fold) and hard-locked (1.4-fold) bolls within the stink bug–infested treatment was significantly greater compared with that in the noninfested treatment. Stink bug injury within hard-locked (1.9-fold) and harvestable (1.7-fold) bolls was more common in the infested treatment compared with those bolls in the noninfested treatment. Stink bugs significantly (1.1-fold) reduced the proportion of harvestable bolls as well as the amount of seedcotton, lint, and seed yield in the infested treatment compared with the noninfested treatment. Significantly more (1.5-fold) seedcotton from hard-locked bolls was collected in the stink bug–infested treatment. Stink bugs reduced germination of seed from harvestable bolls (1.2-fold), but seed germination from hard-locked bolls was not different between treatments. These studies show that southern green stink bug feeding can be associated with higher incidence of rotted and hard-locked bolls when conditions of high rainfall and humidity occur in cotton fields.

The biology of western corn rootworm larvae, Diabrotica virgifera virgifera LeConte, on alternate hosts has become an important topic with the recent commercialization of transgenic-rootworm maize. Larval development and survivorship were monitored on 22 plant species, including maize, Zea mays L.; maize-field weeds; and selected native prairie grasses, fence-row/forage grasses, and small grain crops planted in greenhouse trials. Small pots containing each plant species were infested with 25 western corn rootworm larvae from a nondiapausing strain. Larval recovery was monitored 7, 14, 21, and 26 d after infestation. The dry weight of larvae and adults was recorded in addition to pronotum width of adults and head capsule width of larvae. Larvae survived at least 14 d on 21 species and 26 d on 18 species. Third instars were recovered from 16 species. The head capsule width of larvae recovered from quackgrass, Elytrigia repens L.; Rhodes grass, Chloris gayana Kunth; and fall panicum, Panicum dichotomiflorum Michx, were not significantly different from maize on all four sample days. Adults were recovered from 10 species. These data along with other studies show that almost all grasses tested provide enough nutrition for larvae of the western corn rootworm to survive 14 d, and larval development to the third instar can occur on most grasses. The potential for rootworm larvae to move between weeds within or adjacent to a maize field could be an important factor in resistance management of transgenic-rootworm maize. However, the long-term implication of such movement for a low-dose transgenic event has yet to be worked out

Previous studies suggest that exposure to corn, Zea mays L., anthers expressing Bacillus thuringiensis (Bt)-derived protein may have adverse effects on the larvae of monarch butterfly, Danaus plexippus (L.). To examine the potential effects of Bt anthers on monarch butterflies, studies were designed to test toxicity in the laboratory; examine anther distribution in space and time; compare distributions of anthers, pollen, and larval feeding; and measure effects of long-term exposure in the field. In the laboratory, monarch butterfly larvae fed on whole corn anthers, but anther feeding was sporadic. Larvae exposed to 0.3 anther/cm² fed and weighed less after 4 d compared with larvae exposed to non-Bt anthers. Adverse effects increased with increasing anther density. Monarch butterfly larvae exposed to 0.9 anther/cm² had reduced feeding, weight, and survival and increased developmental time compared with larvae exposed to non-Bt anthers. Later instars were more tolerant of Bt toxin. For all studies, laboratory testing probably magnified effects because larvae were confined to petri dishes. Field studies showed toxic anther densities are uncommon on milkweed (Asclepias) leaves in and near cornfields during anthesis. Mean anther densities on milkweed leaves in cornfields during peak anthesis were between 0.06 and 0.1 anther/cm² (≈ 3–5 anthers per leaf). When exposure to a density of five anthers per leaf was tested in field-cage studies, no effects on growth, development, or survival were detected. Based on probability of exposure to toxic densities, Bt anthers alone are not likely to pose a significant risk to monarch butterflies in Iowa.

Effects on monarch butterfly, Danaus plexippus L., after continuous exposure of larvae to natural deposits of Bacillus thuringiensis (Bt) and non-Bt pollen on milkweed, were measured in five studies. First instars were exposed at 3–4 and 6–7 d after initial anthesis, either directly on milkweed plants in commercial cornfields or in the laboratory on leaves collected from milkweeds in corn plots. Pollen exposure levels ranging from 122 to 188 grains/cm²/d were similar to within-field levels that monarch butterfly populations might experience in the general population of cornfields. Results indicate that 23.7% fewer larvae exposed to these levels of Bt pollen during anthesis reached the adult stage. A risk assessment procedure used previously was updated with a simulation model estimating the proportion of second-generation monarch butterflies affected. When considered over the entire range of the Corn Belt, which represents only 50% of the breeding population, the risk to monarch butterfly larvae associated with long-term exposure to Bt corn pollen is 0.6% additional mortality. Exposure also prolonged the developmental time of larvae by 1.8 d and reduced the weights of both pupae and adults by 5.5%. The sex ratio and wing length of adults were unaffected. The ecological significance of these sublethal effects is discussed relative to generation mortality and adult performance.