The soybean aphid, Aphis glycines Matsumura, has a heteroecious, holocyclic life cycle. Soybean aphids overwinter as eggs, hatch in the spring, reproduce asexually, and undergo three or more generations on buckthorn, Rhamnus spp., before migrating to a secondary host such as soybean, Glycine max (L.) Merr. The ability of different soybean aphid life stages to survive low temperatures potentially experienced during fall or winter is not known. The objectives of this study were to determine the supercooling point (SCP) of various soybean aphid life stages and to determine the annual probability that winter temperatures within the North Central region of the United States would equal or fall below the mean SCP of soybean aphid eggs. Aphid eggs are considered the most cold-hardy stage; therefore, their SCP can be used as a conservative estimate for aphid overwintering mortality. In our study, eggs had the lowest mean SCP (approximately −34°C) among all life stages, whereas gynoparae and oviparae had the highest mean SCPs (approximately −15°C). During the winter, extreme low air temperatures are likely to reach or exceed the mean SCP of soybean aphid eggs in portions of northern Minnesota, northern Wisconsin, and the upper peninsula of Michigan. Thus, widespread successful overwintering in the northern United States and southern Canada is less likely than in Illinois, Indiana, Ohio, Iowa, southern Minnesota, southern Wisconsin, and the lower peninsula of Michigan.

Specific metabolic heat rates (R_q) and respiration rates (R_CO2) of adult Harmonia axyridis Pallas, the multicolored Asian lady beetle, and Hippodamia convergens Guerrin-Manaville, the convergent lady beetle, were measured in isothermal calorimeters at 5°C intervals from 0 to 40°C. Anabolic rates and R_q/R_CO2 ratios were calculated as functions of temperature from the calorespirometric data. The two species have similar heat and CO₂ rates from 0 to 10°C, but both rates are higher for H. convergens at all other temperatures. Anabolic rates and R_q/R_CO2 ratios indicated high-temperature stress in H. convergens at 40°C and at 35 and 40°C in H. axyridis. Anabolic rates and R_q/R_CO2 ratios for the two species differed markedly from 15 to 30°C, where H. convergens had a higher anabolic rate and lower R_q/R_CO2 ratio (i.e., greater metabolic efficiency) than H. axyridis. The data show that H. axyridis maximizes the anabolic rate, and therefore the biosynthesis rate, at low temperatures around 5°C and maximizes the catabolic rate at 25–30°C to support movement. In H. convergens, the optimum temperature range is the same for both biosynthesis (anabolic rate) and movement (catabolic rate), i.e., from 15 to 30°C. The ability of H. axyridis to more efficiently use periods of low temperature for development and reproduction and periods of mid-range environmental temperatures for searching for prey and feeding probably contribute to its competitive displacement of native North American coccinellid species.

The phorid fly, Pseudacteon tricuspis Borgmeier, has been released for biological control of red imported fire ant, Solenopis invicta Buren, in many parts of the southern United States. However, little is known about the nutritional ecology and the effects of environmental and physiological factors on lifespan of adult phorid flies under laboratory or field conditions. Here we report the effects of sugar feeding, temperature, gender, mating, and body size on longevity of P. tricuspis. Sugar availability and temperature were the two major factors influencing longevity. In general, sugar feeding increased lifespan by a factor of 2–3. Longevity of P. tricuspis was inversely related to temperature, and the greatest longevity (≈15 d) was recorded for sugar-fed flies kept at 20°C. Longevity declined from ≈15 d at 20°C to 4 d at 33°C for sugar-fed females and from 7 d at 20°C to 2 d at 33°C for sugar-starved females. Similar results were obtained for male P. tricuspis, and gender or mating did not significantly influence longevity. There was no significant difference in longevity between mated and unmated female and male flies, irrespective of diet and temperature. Gender, however, had a significant effect on wing length with females being larger than males. A positive correlation between wing length and longevity was recorded for sugar-starved female and male phorid flies kept at 20°C and for sugar-starved males kept at 28°C, but not for sugar-fed flies or flies exposed to high temperatures. These results suggest that provision of supplemental sugar sources and suitable microclimate near its release sites may enhance the success of P. tricuspis as a biological control agent.

To determine whether Heliothis virescens and H. subflexa, two closely related sympatrically occurring species, differ in their antennal responses to conspecific and heterospecific pheromone compounds, we recorded electroantennogram (EAG) responses of male and female antennae of both species to eight different compounds loaded on filter paper dispensers. If antennal responses were found to differ in the two species, EAG-recordings from F₁ hybrids and backcrosses between these species could be used in developing an understanding of the genetic architecture of variation in olfactory signal perception. However, all compounds elicited EAG responses in all male antennae tested, and no quantitative differences in response were found between the two species, except for the response to 1 mg (Z)-11-hexadecenol (Z11–16:OH), which elicited larger EAG responses in H. subflexa than in H. virescens males. This difference is consistent with the idea that this pheromone component is less important in the biology of H. virescens. Female antennae of both species were less responsive to the major sex pheromone compound, (Z)-11-hexadecenal (Z11–16:Ald), than male antennae; 10 μg Z11–16:Ald, which elicited strong EAG responses in males, produced female EAGs similar to control puffs of air. However, higher doses of Z11–16:Ald elicited significant EAG responses in female antennae of both species. Female antennae of both species also responded to most other pheromone compounds, except Z11–16:OH. These results support the hypothesis that autodetection of sex pheromones occurs in females of both H. virescens and H. subflexa. Whether females behaviorally respond to any, or to combinations, of these compounds remains to be elucidated.

The synthetic sex pheromone of the pink hibiscus mealybug, Maconellicoccus hirsutus (Green), was evaluated in the field bioassays. In a period of 27 wk, >90,000 males were captured on sticky traps in the three locations in Key Biscayne, FL. Our experimental results showed that a laboratory-prepared (R)-lavandulyl (S)-2-methylbutanoate and (R)-maconelliyl (S)-2-methylbutanoate blend in a ratio of 1:5 on a rubber septum was attractive to males at concentration as low as 0.1 μg per trap. Male M. hirsutus captures were not significantly different from traps baited with 1- or 10-μg doses, but 0.1- and 100-μg doses captured significantly fewer males. Some of the unnatural stereoisomers of the pheromone antagonized attraction. The alcohols, which could be detected in virgin female’s volatiles, also exhibited a repulsive effect. Rubber septum lures baited with 1- and 10-μg doses of the synthetic pheromone remained active for at least 21 wk under field conditions. Monitoring of adult flight activity with a 1-μg dose of synthetic pheromone indicated there were multiple generations during the tested period of 8 July 2003 to 12 January 2004.

Varieties of glandular-haired alfalfa, Medicago sativa L., with resistance to the potato leafhopper, Empoasca fabae (Harris), have been commercially released. To assess the role of volatile organic compounds in leafhopper resistance, stem and leaf volatiles were collected using vacuum steam distillation from the resistant genotype M. sativa G98A and the susceptible M. sativa Ranger. Whole-plant volatiles were collected using head-space analysis. Gas chromatography–mass spectrometry determined that steam distillates from both G98A and Ranger were composed mainly of alcohols and esters, with 1-octen-3-ol, (Z)-3-Hexenyl acetate, and (Z)-3-hexen-1-ol as major components. (Z)-3-hexenyl acetate was the only major component in head-space samples from G98A and Ranger. No volatiles were unique to either G98A or Ranger, but different ratios of volatiles were detected. Two-choice bioassays of leaf steam distillates and head-space samples found significantly more potato leafhoppers oriented toward volatiles from Ranger than G98A. Leafhoppers were attracted to a 0.0001% solution of 1-octen-3-ol, but not to (Z)-3-hexenyl acetate. Instead of producing volatile repellents, resistance of G98A to the potato leafhopper might be based, in part, on decreased attraction.

In native forests in Australia, Mnesampela privata (Guenée) is uncommon, but in plantations, populations can outbreak. Two field trials (GES1 and GES2) were used to test whether oviposition on individual hosts by M. privata increases under plantation conditions of high host abundance. Oviposition on designated target trees was recorded over two consecutive seasons in arboreta where the relative abundance of preferred Eucalyptus hosts decreased, whereas the relative abundance of less preferred or noneucalypt trees increased. Neither trial supported the hypothesis that more eggs are laid on individual hosts when surrounded by trees of the same species. On the contrary, in the third arboretum type in GES2 (lowest relative abundance of eucalypts), more eggs were laid on target eucalypts whose immediate neighboring trees were noneucalypts. The average size of egg clutches increased between 1.3 and 11.7 times from the first to the second season of surveys, and the weight of females increased over the two consecutive seasons, which may have explained the increase in egg clutch size. It is proposed that outbreaks of M. privata occur in eucalypt plantations because high host abundance (and presumably also quality) drives the development of populations that are larger than can be supported by native forests.

Pupae of the blueberry maggot, Rhagoletis mendax Curran, from populations with late flight period develop much faster when placed at constant temperature than when kept outdoors through summer, suggesting that exposure to extreme temperature outdoors may delay adult emergence by causing a heat-induced quiescence. We evaluated the effect of heat exposure on time to adult emergence with pupae of both early and late populations in three experiments. Heat exposure consisted of 12 h at 25°C followed by 12 h at 35°C for different periods of time (10–30 d). In the first experiment, the time to emergence at 20°C was sharply reduced in most samples of pupae of the late population kept in an incubator and exposed to heat relatively early in diapause. However, regardless of the duration of exposure, pupal development always stalled at a threshold of ≈50 d to emergence. In the second experiment, heat exposure increased time to emergence in most samples of pupae of the late population brought from outdoors immediately before the onset of high soil temperature. These pupae also took ≈50 d to emergence after the end of the heat exposure, despite being more advanced in diapause than the pupae in the previous experiment. In the last experiment, short heat exposure accelerated, and longer exposure delayed development of pupae of the early population. As in the previous experiments, emergence occurred ≈50 d after the end of the heat exposure. These results suggest that a heat-induced quiescence is a likely cause for the developmental delay observed in pupae of the late population through summer. Furthermore, the similar time to emergence after heat exposure of both pupae of early and late populations suggests that a discrete quiescence-sensitive period occurs during a specific stage of pupal development in the blueberry maggot. This is the first report of a heat-induced quiescence interrupting diapause development in the blueberry maggot or any Rhagoletis fruit flies.

Phyllobius oblongus (L.), Polydrusus sericeus (Schaller), and Sciaphilus asperatus (Bonsdorff) comprise a complex of nonindigenous root-feeding weevils in northern hardwood forests of the Great Lakes region. Little is known about their detailed biology, seasonality, relative abundance, and distribution patterns. We studied 10 sites over a 2-yr period. Two sites were in northeastern Wisconsin, and eight were in the neighboring southern upper peninsula of Michigan. Larval abundance was estimated by soil sampling, and adult abundance was estimated by sweep netting, emergence trapping, and beating samples. Sweep netting collected the most weevils overall (71.0%), whereas beating and emergence traps collected 22.1 and 6.9%, respectively. P. sericeus were the predominant larvae, representing 34.3% of total Curculionidae, whereas P. oblongus were the predominant adults, representing 66.4% of Curculionidae. Few S. asperatus and Trachyphloeus aristatus (Gyllenhal) larvae and adults were collected, with the latter being a new record for Wisconsin. Two additional species, Barypeithes pellucidus (Boheman) and an undetermined Polydrusus sp., were collected only as larvae. Six species of curculionids were collected overall, with at least five being confirmed as nonindigenous species. P. oblongus and P. sericeus adults were the most abundant. These did not coincide temporally. Over 63% of P. oblongus and P. sericeus were collected during single 4-wk intervals in mid-June and mid-July, respectively. Conversely, S. asperatus adults overlapped with both other species, occurring sparingly from 4 June through 28 August. One species was predominant at each site and generally accounted for ≥80% of the total weevil population. P. oblongus larvae and adults predominated in five and eight sites, respectively, whereas P. sericeus and S. asperatus larvae and adults predominated in one site each. Adult and larval populations were generally clustered. We evaluated vertical stratification of P. sericeus larvae in the soil, and most were located within the top 10 cm.

We studied the developmental performance of the large biotype of Pseudacteon obtusus Borgmeier, a promising biological control agent of imported fire ants. We measured selected life history traits of this parasitoid as a function of (1) host species (Solenopsis invicta Buren versus Solenopsis richteri Forel), (2) temperature (22 versus 28°C), and (3) size distributions of available host ants (big versus mixed-size classes of workers). Survivorship on S. invicta was much greater than that on S. richteri under most conditions. Developmental time was strongly influenced by temperature with total developmental periods shortened by 21–34% at the 6°C higher temperature treatment. However, developmental periods were weakly influenced by hosts across temperatures. We found that larval, pupal, and total developmental periods of this phorid fly were up to 6.2% longer on S. richteri than on S. invicta, although these periods depended on temperature. Total developmental time was slightly shorter (by 4.8%) on S. invicta than S. richteri at 22°C but longer (by 5.7%) on S. invicta at 28°C. The relationship between host size and sex of emerging flies contrasts with that of previously documented Pseudacteon species, in that males were produced from all host size classes while females only came from larger ants. Sex ratios favor females when a mixture of ant size classes were offered in comparison to when only big ants could be chosen. Pseudacteon obtusus seems to be a promising candidate for biological control releases in that in addition to its high host specificity, it develops better on red fire ants, attacks ants on trails and mounds, and chooses a worker size range that complements the two other Pseudacteon species already released.

The paucity of empirical data on processes in species life cycles demands tools to extract insight from field observations. Such insights help inform policy on invasive species and on impacts of climate change at regional and local scales. We used the CLIMEX model to infer the response of the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae), to temperature and moisture from its range in the United States. We tested hypotheses on the mechanisms that limit the distribution of the ant and estimated the potential global area at risk from invasion. The ant can spread further in the United States, including north along the west coast, where patterns of infestation will differ from those in the east. We analyzed the risk of colonization in Australia and New Zealand, where the ant was recently discovered. The patterns of infestation of the ant in Oceania will differ from those in the eastern United States, with slower growth and less winter mortality. This study adds to earlier temperature-based models by incorporating a moisture response; by replacing arbitrary categories of colony size to predict overwintering success with a site-specific model based on the balance between annual growth and survival; and by comparing different hypotheses on low temperature-related mechanisms that limit the geographical distribution. It shows how the response of a species to climate can be synthesized from field observations to provide useful insights into its population dynamics. Such analyses provide a basis for making decisions on regional management of invasive species and an informative context for local studies.

Macrocentrus iridescens French is a polyembryonic parasitoid with a wide host and geographic range in North America. In a survey of California pistachio orchards, M. iridescens was the most common parasitoid species reared from the obliquebanded leafroller, Choristoneura rosaceana Harris. To determine its potential as a biological control agent of the obliquebanded leafroller, we conducted laboratory studies and described M. iridescens immature development. We evaluated adult female longevity, brood size, sex ratio, and host stage preference for oviposition. The parasitoid egg develops polyembryonically. At 26.8°C, larval development required 25–30 d, and pupal development 10–12 d. There was a positive relationship between mandible size and development time, although individual stages could not be determined. Adult females survived on average 15.9, 1.6, and 0.9 d at 25°C when provided with honey and fructose solution, water only, or neither, respectively. Oviposition of fertilized eggs was observed 24 h after adult eclosion, and continued for 27 d. Under laboratory conditions, each brood produced an average of 27.2 adult M. iridescens. More broods were of mixed gender (56%) than exclusively male (17%) or female (27%), with an average of 30.9, 25.8, and 20.2 adult M. iridescens per brood, respectively. M. iridescens oviposited in all host larval stages, with significantly more second (26.6%) and third (42.2%) instar larvae parasitized than first, fifth, or sixth instars. The potential of mass rearing and augmentative release of M. iridescens is discussed.

The seasonal occurrences of Macrocentrus cingulum Brischke and its host, Ostrinia nubilalis Hübner, were studied. Overwintering fifth-instar O. nubilalis were collected from the field in 1997, 1998, 2001, and 2002 and reared under controlled laboratory conditions to determine pupation and adult eclosion periods for M. cingulum and O. nubilalis. In addition, pheromone and yellow sticky traps were established in the field in 2001 and 2002 to monitor adult activity of O. nubilalis and M. cingulum. Mathematical equations were constructed based on the laboratory and field data. The equations confirmed the temporal co-occurrence of M. cingulum and O. nubilalis adults. However, third- and fourth-instar O. nubilalis, the preferred host stages of M. cingulum, occur later in the growing season. The timing of M. cingulum adult life expectancy and the occurrences of its preferred host stages in the field were predicted using the equations, published degree-day requirements for O. nubilalis and information from the literature on adult M. cingulum longevity. When the predicted period of M. cingulum adult activity was compared with the predicted timing of third- and fourth-instar O. nubilalis, M. cingulum adult presence was synchronized with preferred host stages.

We have combined aircraft and airborne Doppler radar observations to show that microinsects in the atmospheric convective boundary layer (CBL) are concentrated in rather well-defined plumes, that these plumes are generally found in thermals of rising air, and that the insects in those plumes oppose the updrafts at a rate that increases as the updrafts become stronger. In this paper, a simple numerical simulation of the airflow field and insect concentration in the CBL is developed. The model shows a consistency of the observed insect flight behavior with the presence of well-defined insect plumes in the otherwise well-mixed CBL and with the tendency of insects to cluster in updrafts. The model also explains the growth of insect plumes in the morning hours and their disappearance in the late afternoon. Other studies have proposed that the response of insects to being lofted high into the CBL is controlled by air temperature. Our simulation shows that a temperature-sensitive response alone does not yield well-defined plumes in regions of rising air currents. The observed flight strategy may be counterintuitive, but we suggest that it has a clear adaptive advantage.

The vertical flight behavior of insects in the convective boundary layer (CBL) is examined by means of profiling airborne Doppler radar data collected in the central Great Plains in late spring. On fair-weather days, the CBL grows from the ground up in morning hours and matures at a depth of 1,000–1,500 m shortly after midday. It is well mixed by thermals bubbling up from near the surface. Nevertheless the CBL is dominated, over its entire depth, by well-defined regions of high insect concentrations, here referred to as insect plumes. This is inferred from radar, whose echoes in the CBL are largely caused by microinsects (<10 mm diameter). This study focuses on the vertical motion of the radar scatterers relative to the vertical air motion, in natural conditions. It is shown that insect plumes tend to be collocated with updrafts in the CBL and that microinsects tend to fall or fly down against the updrafts at an average speed of 0.5 ± 0.2 m/s. This estimate is based on a comparison of the close-range radar velocities, some 100 m above and below the aircraft, with the vertical air velocity measured at flight level. We hypothesize that the gregarious behavior of small insects in the CBL is explained by their tendency to oppose updrafts at a rate that is surprisingly proportional to the updraft strength. This finding is also strong evidence for the biotic nature of the echo plumes. This hypothesis is tested elsewhere by means of a simple numerical simulation.

Seasonal patterns of ground beetle activity were examined at six highbush blueberry (Vaccinium corymbosum L.) farms in southwestern Michigan. On each farm, pitfall traps were used to monitor ground beetle activity in two adjacent fields: one managed under a conventional insecticide program (grower standard) and the other with reduced-risk insecticides. Overall, more active ingredient was applied in grower standard than reduced-risk fields, with the greatest amount used in June and July. During the 6-mo sampling period, we collected 11,322 ground beetles comprised of 34 species, with Harpalus pensylvanicus DeGeer representing 70.7% of the total beetles collected. The greatest amount of ground beetle activity occurred in August and September, mostly because of increased captures of the autumn breeding species H. pensylvanicus and H. erraticus Say. Only H. erraticus responded to the different insecticide programs, with eight-fold greater captures in reduced-risk compared with grower standard fields. Because H. erraticus are in the soil as larvae or pupae during June and July, we suggest that greater insecticide use in the grower standard fields resulted in increased mortality of immature H. erraticus. At one farm, where ground cover was absent between blueberry rows, H. erraticus activity did not respond to the difference in insecticide program. This suggests that enhancement of ground beetle activity may require suitable habitat in addition to a reduction in broad-spectrum insecticide use.

Corn engineered to produce the Cry3Bb1 protein from Bacillus thuringiensis (Bt) kumamotoensis has provided unprecedented control for corn rootworm (Diabrotica spp.). However, the Bt protein may be released in soil by root exudates or decaying plant residues that may affect soil organisms. Field studies were conducted to determine the abundance of surface and below-ground nontarget arthropods in fields planted with Bt or non-Bt corn for the first year or planted over 3 consecutive yr. Results of these studies showed that there were no significant differences in numbers of surface and below-ground arthropods in soil planted with Bt and non-Bt corn at any of the studied locations. Enzyme-linked immunosorbent assay (ELISA) showed no detectable Cry3Bb1 protein in any of the soil samples collected in a field planted with a Bt corn hybrid and its non-Bt isogenic hybrid for the first year or planted over 3 consecutive yr near Manhattan, KS. However, a small amount of Cry3Bb1 protein (3.38–6.89 ng/g dry soil) was detected in the soil samples collected from an area near plants in a Bt corn field that was planted for the first year near Scandia, KS. These findings indicate that the Cry3Bb1 protein released from root exudates or decaying plant residues does not persist and is rapidly broken down in the soil. The rapid degradation of Cry3Bb1 in soil results in none or trace amounts of protein being detected by ELISA.

Malaise and pitfall traps were used to sample herbivorous insects in canopy gaps created by group-selection cutting in a bottomland hardwood forest in South Carolina. The traps were placed at the centers, edges, and in the forest adjacent to gaps of different sizes (0.13, 0.26, and 0.50 ha) and ages (1 and 7 yr old) during four sampling periods in 2001. Overall, the abundance and species richness of insect herbivores were greater at the centers of young gaps than at the edge of young gaps or in the forest surrounding young gaps. There were no differences in abundance or species richness among old gap locations (i.e., centers, edges, and forest), and we collected significantly more insects in young gaps than old gaps. The insect communities in old gaps were more similar to the forests surrounding them than young gap communities were to their respective forest locations, but the insect communities in the two forests locations (surrounding young and old gaps) had the highest percent similarity of all. Although both abundance and richness increased in the centers of young gaps with increasing gap size, these differences were not significant. We attribute the increased numbers of herbivorous insects to the greater abundance of herbaceous plants available in young gaps.

This paper links ecological theory to the biological control of insect pests in banana plantations. Through an established predictive approach, ecological data on tritrophic interactions from natural systems were used to formulate simple recommendations for biological control in banana plantations. The specific goals were (1) to determine the most effective parasitoid enemies for biological control of lepidopteran larvae in banana plantations and (2) to examine the impact of nematicides on enemy populations. To assess percent parasitism, we reared 1,121 lepidopteran larvae collected from six plantations managed under two nematicide regimens. Attack by parasitoids in the families Tachinidae (Diptera), Braconidae, Eulophidae, and Chalcididae (Hymenoptera) closely paralleled rates reported for species with similar characteristics in lowland wet forests, and statistical models predicted the relative importance of these parasitoids as sources of mortality. We found that tachinid flies were the most important source of early instar larval parasitism in banana plantations, and their importance increased with more intensive nematicide applications. The statistical models that we derived from data on natural systems were useful in predicting which parasitoids would be important in banana and which larval characteristics they would preferentially attack. This approach could be used in other managed ecosystems where the identification of effective biological control agents is needed.

An invasive, exotic coccinellid, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), was recently identified as a potential hazard to immature monarch butterflies, Danaus plexippus L. (Lepidoptera: Nymphalidae). To further evaluate the risk of H. axyridis impacting D. plexippus, we evaluated the influence of an alternate prey, Aphis nerii Boyer de Fonscolombe (Homoptera: Aphididae), on the predation rate of H. axyridis on D. plexippus larvae. When first-instar D. plexippus were placed in petri dish arenas with third-instar H. axyridis and varying densities of A. nerii, D. plexippus survival after 24 h increased significantly from 0% with 0 A. nerii present to 73% with 30 A. nerii present. In predation studies conducted in field cages, survival of D. plexippus larvae decreased with increasing densities of H. axyridis larvae and tended to increase with increasing A. nerii densities. These studies indicate that H. axyridis will feed on D. plexippus larvae in the presence of A. nerii, but that the presence of A. nerii lessens the severity of predation on D. plexippus.

We followed the daily and seasonal foraging patterns of the solitary bee Proxylocopa olivieri during two springs and summers in Har Gilo, Israel. During the foraging season, the bees exhibited a clear bimodal daily activity pattern. They foraged mostly before sunrise and after sunset. We hypothesized that this activity schedule entails foraging benefits. We found that snapdragon (Antirrhinum majus L.) was a major source of nectar for P. olivieri. Nectar production rates in snapdragon were significantly higher during the morning activity period of P. olivieri than during mid-day. Bees of numerous other species foraged on snapdragon, but their activity periods hardly overlapped with P. olivieri. Foraging activity in P. olivieri was highest at a combination of high (25–35°C) temperatures and low (1–100 Lux) illumination levels. We suggest that P. olivieri benefits from foraging at dawn and dusk on snapdragon, and possibly additional food plants, because of exploitation of the large amounts of nectar produced. A nectar enrichment experiment revealed that P. olivieri does not cease foraging because of lack of available nectar. We suggest that the P. olivieri’s ability to fly at low light levels enables it to dominate a unique foraging niche.

The multicolored Asian lady beetle Harmonia axyridis (Pallas) is often a pest during autumn, when large numbers take flight and subsequently land on and enter buildings. Open field experiments were conducted during the autumn flight to examine the role of linear contrast in visually attracting beetles. White targets printed with 61 by 15-cm stripes that varied in orientation and degree of contrast were covered in insect adhesive, attached to a white background panel, and erected in sites known to be attractive to flying beetles. Flights occurred when temperatures rose above 21°C. Diurnally, peak flight occurred between 1400 and 1600 hours but shifted progressively earlier within that framework as the flight season advanced. Beetles significantly chose targets with high contrast, black stripes; the number of beetles landing on all other contrast levels did not differ significantly from controls. Vertically positioned stripes attracted more beetles than horizontal ones, but not significantly. The effects of high contrast were absolute rather than relative. The number of beetles landing on targets with 50% contrast stripes did not increase when these were the highest contrast targets available. Results suggest that visual intensity contrast is key to understanding the behavior of H. axyridis in autumn and call into question some commonly accepted ideas regarding choice of overwintering sites. First, during migratory flight, H. axyridis is not visually attracted to the color white per se, and second, it is unlikely that, during flight, pheromones are involved in beetle orientation.

Most central Honshu populations of the ladybird beetle, Coccinella septempunctata L., pass the winter as quiescent adults. However, variations in life cycle within populations have been observed: hibernating and reproductive adults simultaneously coexist in the same habitat in winter. We studied microhabitat use patterns of this beetle in winter on a sunny slope of a southeast-facing riverbank. We found that, even though natural substrates were available, the beetle preferred to use artificial substrates such as metal cans (iron or aluminum), papers, and wooden materials discarded on the slope as oviposition and pupation sites. The artificial substrates were relatively easily warmed by solar radiation and were therefore used as thermal microhabitats by the beetle. Although ambient winter air temperatures of this region were not high enough for the beetles to complete their development, the use of thermal microhabitats enabled them to do so by thermal conduction. Prey aphids were also abundant during the winter. Thermal microhabitat use enables these beetles to complete an additional generation in winter.

Previous research has shown that more Coleomegilla maculata (DeGeer) eggs occur on plants with glandular trichomes than on plants without such trichomes. Those studies also revealed that C. maculata eggs suffer greater predation (mostly cannibalism) on plants lacking glandular trichomes than on plants with glandular trichomes. Those results, however, left open the question of whether differences in observed egg densities on the two types of plants were caused by oviposition preference or differential removal of eggs by predators. Our primary objective was to determine whether C. maculata preferentially oviposit on plants with glandular trichomes. We also determined the diel periodicity of C. maculata oviposition; in addition to its intrinsic value in understanding the predator’s behavior, this knowledge facilitated our study of oviposition preference. Diel periodicity of oviposition was studied in the laboratory and in the field. In the laboratory, most oviposition occurred in the afternoon and early evening. In the field, the pattern was even more distinct, with all oviposition occurring between 1200 and 2000 hours and >80% occurring between 1400 and 1800 hours Eastern Daylight Time. To determine oviposition preference, we placed equal numbers of velvetleaf, Abutilon theophrasti (Medicus), and smooth pigweed, Amaranthus hybridus L., plants (with and without glandular trichomes, respectively) in the field and observed them continuously during the afternoon and early evening. Oviposition events by naturally occurring (i.e., wild, uncaged) C. maculata were recorded. The beetles clearly preferred to oviposit on plants with glandular trichomes, laying 51 of 52 egg clusters on velvetleaf, despite the fact that they visited smooth pigweed plants more often and spent more time per visit on those plants than on velvetleaf. We hypothesize that egg predation, especially cannibalism, has selected for this oviposition behavior.

The objective of this project was to quantify the spatial structure for the Colorado potato beetle in a northern region. The study was carried out in 15 sections of 10 ha of commercial potato fields and six 1-ha experimental fields in New Brunswick between 1999 and 2001 using a 20 by 20-m sampling grid. The sampling sites occupied by adults, expressed as a percentage of sites available for colonization at even distances from the nearest field border, tended to be distributed uniformly across the field area. The study confirmed the applicability of the curvilinear relation between beetle incidence and mean density per sample to Canadian insect populations. A significantly larger proportion of the postdiapausing and prediapausing adult potato beetles was found nearest field borders. This larger proportion of adults was shown to result largely from the greater number of sites (or plants) available for colonization at the outside perimeter of fields than at any other distance within the fields but also from an accumulation or redistribution of a small percentage of the adults to the first 0–20 m of the crop along a field border. The ability of the adult potato beetles to extend their presence over most of the field area at the very beginning of the crop season, when their abundance is low, limits the value of perimeter control methods against this pest. However, accumulation of individuals around the perimeter does justify their use for larger fields and if control measures are applied up to 20–40 m from the edge. Spatial dependency was present in only 1–7% of the monitoring dates and explained between 0 and 68% of the variation. The generation of distribution maps for site-specific management of the Colorado potato beetle, Leptinotarsa decemlineata (Say), does not seem to be a practical alternative to existing sampling programs.

For parasitoids of herbivores, the two most important biotic factors that will influence their fitness are the host species that they attack and the plant species that the host feeds on. Variation in these two trophic levels because of different habitat characteristics may largely drive the evolution of the interaction between parasitoids and their hosts. Through transplant experiments with three plant–insect populations in Mexico, we examined the consequences of plant variation for the interaction between a bruchid beetle, Zabrotes subfasciatus (Boheman) (Coleoptera: Bruchidae), that feeds on bean seeds of the genus Phaseolus L. (Leguminosae: Phaseolinae) and one of its main parasitoids, Stenocorse bruchivora (Crawford) (Hymenoptera: Braconidae). Results revealed great variation in performance among parasitoid populations. Both the population of origin of the parasitoid and of the host plant influenced the performance of developing parasitoids as well as adult oviposition behavior. Wasps from the Atila population were more likely to parasitize the herbivore and developed faster than wasps from the other two populations, Malinalco and Tepoztlan. The results can be explained in part by the spatial distribution of the host plant, host availability, and seed quality in this population. Variation in performance among parasitoid populations decreased when wasps were exposed to their host in cultivated seeds. This could be caused by the better and less variable quality of this novel resource, and consequently, of the bruchid host. The results from this study indicate that both host plant quality and genetic variation among populations are crucial factors in determining the nature and evolution of the interaction between parasitoids and their herbivorous hosts.

The abundance of Homalodisca coagulata (Say) (Hemiptera: Cicadellidae) was examined in north Florida from 2001 to 2003 on the following Vitis genotypes: V. rotundifolia Michx. (cultivars ‘Carlos’, ‘Early Fry’, ‘Regale’, and ‘Noble’), V. rupestris Scheele. (cultivars ‘St. George’ and ‘Constancia’), V. simpsoni Munson (cultivar ‘Pixiola’), V. champini Planch. (cultivars ‘Dogridge’ and ‘Ramsey’), and V. vinifera L. (cultivars ‘Chardonnay’, ‘Chenin blanc’, and ‘Exotic’). The mean number of adult H. coagulata was less than two per vine per day during 2001 and was lowest on V. rotundifolia cultivars. During June/July 2002, the number of leafhoppers varied between 2 per vine per day on V. rotundifolia cultivars and 10–20 per vine per day on the other Vitis genotypes. The distribution of H. coagulata was examined from June to September 2002 and during August 2003 in relation to the primary organic nutrients (19 amino acids, 7 organic acids, and 3 sugars) in xylem fluid. The concentrations of most amino acids varied with Vitis genotype. Glutamine represented between 58 and 89% of all amino acids. Leafhopper abundance was positively correlated with total amino acids and percentage glutamine and inversely correlated with many of the remaining amino acids. The percentage of proline in xylem fluid was the best inverse correlate to leafhopper abundance during 2002 and 2003. Consumption rates of H. coagulata were positively correlated to insect abundances. The adult to nymph ratio was over 10:1, and egg masses were only occasionally found on Vitis. These data suggest that adult H. coagulata used Vitis primarily as a feeding host. The ratio of glutamine to proline (GlnPro) was the most consistent chemical correlate to H. coagulata abundance and feeding. Glutamine and proline may play a behavioral role in determining H. coagulata host selection and consumption rates.

Increased concentrations of CO₂ and ozone are predicted to lower nutritional quality of leaves for insect herbivores, which may increase herbivory as insects eat more to meet their nutritional demands. To test this prediction, we measured levels of herbivory in soybean grown in ambient air and air enriched with CO₂ or O₃ using free air gas concentration enrichment (FACE). Under open-air conditions and exposure to the full insect community, elevated [CO₂] increased the susceptibility of soybeans to herbivory early in the season, whereas exposure to elevated [O₃] seemed to have no effect. In the region of the canopy exposed to high levels of herbivory, the percentage of leaf area removed increased from 5 to >11% at elevated [CO₂]. We found no evidence for compensatory feeding at elevated [CO₂] where leaf nitrogen content and C:N ratio were unaltered in plants experiencing increased herbivory. However, levels of leaf sugars were increased by 31% at elevated [CO₂] and coincided with a significant increase in the density of the invasive species Popillia japonica Newman (Japanese beetle). In two-choice feeding trials, Japanese beetles and Mexican bean beetles (Epilachna varivestis Mulsant.) preferred foliage grown at elevated [CO₂] to foliage grown at ambient [CO₂]. These data support the hypothesis that the increased level of sugar in leaves grown at elevated [CO₂] may act as a phagostimulant for the Japanese beetle. If these results apply more widely to soybean production, the expectation of agricultural yield increases as a result of increasing elevated [CO₂] may need to be reevaluated.

Conifer resin and phloem tissue contain several phytochemical groups, composed primarily of monoterpenes, diterpene acids, and stilbene phenolics. The effects of monoterpenes and phenolics on stem-colonizing bark beetles and their associated microorganisms have been studied to some extent, but the roles of diterpene acids are largely unknown. Diterpene acids are known to have substantial feeding deterrent and growth inhibiting effects on a variety of insect groups and are known to inhibit a variety of fungi. We tested three diterpene acids present in red pine, Pinus resinosa, at various concentrations, on several life history components of the bark beetle Ips pini and the fungus Ophiostoma ips. No diterpene acid affected the host acceptance behavior or larval survival of Ips pini. In contrast, abietic acid and isopimaric acid strongly inhibited spore germination of O. ips, and abietic acid strongly inhibited mycelial growth. The levels of inhibition observed were higher than with any previous assays of monoterpenes or phenolics in this system. These results support the view that conifer defenses against bark beetle–fungal complexes are multifaceted, with all three phytochemical groups being important to P. resinosa, but each with varying relative activity against the beetles and fungi.

The western corn rootworm (Diabrotica virgifera virgifera LeConte) (Coleoptera: Chrysomelidae) is a major corn insect pest in North America and is spreading in Europe. Seven polymorphic microsatellite loci were surveyed to characterize genetic structuring of D. v. virgifera populations, based on 595 individuals sampled from 10 locations across nine U.S. states (western Texas and Kansas to New York and Delaware). All populations showed high levels of genetic diversity, with mean allelic diversity ranging from 7.3 to 8.6, and mean expected heterozygosity ranging from 0.600 to 0.670. D. v. virgifera populations exhibited little genetic differentiation as a whole across the geographic range sampled, with a global F_ST of only 0.006. Pairwise F_ST estimates also revealed little genetic differentiation among populations. Most pairwise F_ST values were nonsignificant, except for those estimated between the Texas population and all others. There was a positive correlation between genetic distance and geographic distance as a whole, but no significant correlation for populations from Kansas to the east coast. There was no evidence for a genetic bottleneck in any D. v. virgifera population sampled. Phylogenetic and principal component analyses support the picture of high genetic similarity over much of the United States. Although high migration rates could produce the same pattern and cannot be ruled out, it seems more likely that the D. v. virgifera populations sampled have had insufficient time for substantial genetic structuring to develop since its recent eastward range expansion from the Great Plains that began ≈50 yr ago.

Determining the origins of invasive species has important management implications when introduced species become pests, especially when candidate biocontrol agents are specialized on host biotypes. The cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham), is a European native that was first discovered in North America in British Columbia in 1931. It has since become a major economic pest of brassicaceous oilseed crops. To assess population structure and determine points of origin for North American introductions, we sequenced a 475-bp fragment of the mitochondrial DNA COI gene in 176 individuals from 16 localities from North America and Europe. Eleven haplotypes were found, with one haplotype present in every locality and represented by 71% of all individuals. Nested clade analysis indicated fragmentation, range expansion, restricted gene flow, and long distance dispersal. Analysis of molecular variance (AMOVA) also showed significant population structure and supported an inference of restricted gene flow between populations. These patterns may be explained by two separate introductions to North America. The first introduction was to western North America from source locations likely to have been western or northern Europe, and the second was to northeastern North America from locations, such as Sweden or Russia, that are distinct from the first introduction. At least two females were introduced to western North America, and three to northeastern North America, where the species was recently detected in Quebec.