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The sterile insect technique (SIT) is widely used to suppress or eradicate tephritid fruit fly pests that threaten agricultural crops. The SIT entails the production, sterilization, and release of large numbers of the target pest species, with the goal of achieving sterile male by wild female matings, which result in infertile eggs and the subsequent reduction of the wild pest population. The success of this control strategy depends, to a large extent, on the ability of released, sterile males to compete successfully against wild males to achieve copulations with wild females. Lance and McInnis (2005) proposed that species with greater male involvement in courtship and mating are less amenable to the SIT than species with simple courtship, because strong artificial selection characteristic of mass-rearing environments is more likely to generate greater behavioral modification to complex than simple courtship and thus to result in increased rejection by wild females. Consistent with Lance and McInnis (2005), the mating competitiveness of mass-reared males of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), a species with complex male courtship, is substantially lower than that of mass-reared males of the melon fly, Bactrocera cucurbitae (Coquillett), or the oriental fruit fly, Bactrocera dorsalis (Hendel), two species with very simple male courtship. In light of this difference in mating ability, we tested the prediction that higher overflooding ratios (sterile:wild males; OFR) would be required to control populations of C. capitata than of the Bactrocera spp. Levels of induced egg sterility achieved under different OFRs were compared to the “net sterility target,” computed as the proportional decrease in a lspecies' intrinsic birth rate (realized via SIT) required to balance the intrinsic rate of death and found to be ∼80% for the three species considered. Although the data are scant, they generally support the prediction. For B. cucurbitae, OFRs < 50:1 resulted in egg sterility levels near 80%, whereas in C. capitata similarly high sterility values were achieved only with OFRs >300:1. Likewise, relative to populations in control (untreated) sites, populations in release areas were reduced >99% at OFRs of 50:1–100:1 for B. cucurbitae in Japan compared to reductions for C. capitata of 50–93% at OFRs between 700:1–3,160:1 in Nicaragua and about 80% for OFRs between 100:1–400:1 in Hawaii. The implications of these findings for fruit fly SIT are discussed.
Herbivorous insects can be an important part of weed management, but it is necessary to understand the life history of the organisms involved and how they interact. This is especially pertinent when dealing with endophagous insects with restricted mobility. Hadroplontus litura F. is a stem-mining weevil that is considered a biological control agent of Canada thistle (Cirsium arvense L.), a perennial weed that forms clonal networks. We investigated the biology of H. litura and its association with Canada thistle at six field sites along a latitudinal gradient over 2 yrs, including documenting immature phenology and feeding damage, quantifying immature life stages, and exploring relationships between weevils and shoot size as well as weevil density and feeding damage. Eggs were present until the beginning of June and third-instar larvae began to exit shoots in mid-June, although some were present in July. It appeared that adult females laid more eggs on larger shoots, and preferred shoots not previously used for oviposition. The head capsule size of third instars was not correlated with shoot size, but it was positively related to larval density. Overall, infested shoots had an average of four weevil immatures, although densities ranged up to 21. Larval density was positively associated with stem damage, and both parameters appeared to be more intense at our sites than previous reports. Understanding how the intensity of larval damage impacts Canada thistle plants over time is critical to understanding the relevance of these insects for weed biocontrol.
The biology and ecology of Psyllaphycus diaphorinae Hayat, a potential natural enemy of the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is poorly understood. In April 2013, six P. diaphorinae females collected from Punjab, Pakistan emerged from parasitized Asian citrus psyllid nymphs in quarantine at the University of California, Riverside and were used to initiate colonies. Contrary to previous claims, P. diaphorinae was found to be an obligate hyperparasitoid and not a primary parasitoid attacking Asian citrus psyllid nymphs. P. diaphorinae was able to successfully reproduce on both Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae) and Diaphorencyrtus aligarhensis (Shafee, Alam, and Agarwal) (Hymenoptera: Encyrtidae) pupae, both primary parasitoids of Asian citrus psyllid. No reproduction on unparasitized Asian citrus psyllid nymphs was observed. D. aligarhensis appears to be a preferred host in comparison to T. radiata, as P. diaphorinae produced a higher number of offspring and a higher proportion of females on D. aligarhensis.
Climate warming in the coming decades may affect diapause in insect species which use it to survive unfavorable winter conditions. Plebeia droryana (Friese) (Hymenoptera: Apidae: Meliponini) is a highly eusocial bee species that exhibits reproductive diapause and inhabits southern South America where winter temperatures may fall below 10°C, or even below 0°C in extreme years. In this paper, we evaluate whether P. droryana might terminate diapause during winter under laboratory conditions. We initially kept colonies of P. droryana at 8°C in a biochemical oxygen demand chamber, and then raised the temperature by 2°C every 3 d until the cessation of diapause was detected, as indicated by the onset of brood cell building and subsequent egg-laying by queens. We found that the termination of diapause in P. droryana could be achieved at temperatures between 16°C and 22°C, resulting in typical postdiapause brood cell building and egg-laying rates. Our binomial generalized linear mixed model indicated that only temperature, but no time or temperature–time interaction, explained the probability of termination of diapause in P. droryana. Again, only temperature, but no time or temperature–time interaction, significantly affected amount of brood cell built postdiapause in this species. These data suggest that the levels of predicted climate warming in the geographic range of P. droryana over the coming decades will probably result in these populations abandoning diapause behavior. These results have important implications regarding the ecological service of crop and wild plant pollination provided by this species.
Sexual receptivity and mating behavior of the cabbage aphid parasitoid Diaeretiella rapae McIntosh were studied under laboratory conditions. When male and female D. rapae were paired females, males actively courted females, while females kept themselves away from males and displayed grooming behavior. Males became sexually active immediately after emergence and made mating attempts, whereas females took longer to become receptive to mating. Virgin males quickly detected female presence, resulting in a significant increase in the frequency of male courtship. Males encountered females within 5 min of pairing, and 90% of the males displayed courtship behavior by fanning their wings and chasing the female for mating. Before successful mating, males tended to approach females more often than females approached males. The time between pairing and mating in newly emerged females was longer than in 1-d-old females. The overall mating success in D. rapae was about 70%, and successful mating was largely dependent on females' decision to mate. Unlike females, males remained sexually receptive after mating.
A new species of DineutusMacleay, 1825 is described from the Southeastern Coastal Plain of the United States. Habitus and aedeagus images as well as illustrations of elytral apices, protarsus, palps, and male mesotarsal claws are provided for Dineutus shortin. sp. and compared to those of D. discolor Aubé, 1838. The importance of the southeastern Coastal Plain as a biodiversity hotspot and the potential conservation concern of D. shortin. sp. also are discussed.
Insect-induced plant galls are thought to provide gall-forming insects protection from predation and parasitism, yet many gall formers experience high levels of mortality inflicted by a species-rich community of insect natural enemies. Many gall-forming cynipid wasp species also display heterogony, wherein sexual (gamic) and asexual (agamic) generations may form galls on different plant tissues or plant species. Despite broad interest in using these systems to study parasitism, enemy escape, and community assembly, few studies have provided complete characterizations of the natural enemy diversity associated with gall-forming wasp species, and fewer still have done so for both alternating generations. Here, we characterize the parasitoids, inquilines, and hyperparasitoids associated with the alternating sexual and asexual generations of the cynipid gall former, Belonocnema treatae Mayr in Texas, USA. We find 24 species associated with the asexual generation in leaf galls and four species associated with the sexual generation in root galls. We provide photographs and mitochondrial sequences for most species, discuss implications of these findings for hypotheses that consider heterogony as an adaptation for escape from natural enemies, and contemplate the relative incidence of specialized versus generalist feeding habits among gall former natural enemies.
This study examined temperature preferences of four subterranean termite species, Coptotermes gestroi Wasmann, Coptotermes formosanus Shiraki, Reticulitermes virginicus (Banks) and Reticulitermes flavipes (Kollar), and effects of temperature on their survivorship and wood-consumption rate. Termite preference was tested on temperature gradient along a metal bridge divided into 12 zones. The number of termites in each zone was recorded to compute mean temperature preference values. The result showed that active C. gestroi, C. formosanus, R. virginicus and R. flavipes were found in temperature ranges of 13.0–38.6, 9.3–38.1, 8.2–36.7 and 5.2–34.0°C, respectively. Reticulitermes spp. preferred significantly lower temperatures than Coptotermes spp. Within the temperature range of 20–25°C, survivorship and wood-consumption rate were not significantly different among four species. R. flavipes survived at 10°C but not at 35°C. C. gestroi did not survive at 10°C, but the wood-consumption rate at 35°C was significantly higher than those of other temperatures in the range of 15–30°C. The results account for the geographic distributions of the four termite species and may be used to predict the potential areas of non-native invasions.
Forensic entomology field researchers have typically placed experimental carcasses ≤50 m apart. Direct observations indicate that this intercarcass distance sufficiently prevents cross contamination by crawling larvae, but seems insufficient to prevent highly mobile adult insects from detecting or visiting more than one carcass. It would be valuable if minimum intercarcass distance ensured independence of replicates, because this is an assumption of common statistical analyses. For 32 domestic pig carcasses exposed during two consecutive summers (range of intercarcass distance 30 to >300 m), possible relationships between: 1) average distance to another carcass and aspects of the succession patterns of forensically important species and 2) intercarcass distance and community similarity indices were estimated with regression analyses. In addition, minimum intercarcass distance was investigated through semivariogram analyses of aspects of the succession interval as well as community similarity indices. Pairwise similarity of time to first occurrence was the only variable that displayed a consistent, in this case negative, relationship to intercarcass distance, although not statistically significant for any single analysis. Semivariogram analysis suggested that under the conditions used for our experiment commonly used intercarcass distances are satisfactory to ensure independence of carcasses.
Olive fruit fly, Bactrocera oleae Rossi, is a worldwide pest of olives. To discover new parasitoids for a biological control program in California, olives were collected from various locations in the Himalayan foothills (China, Nepal, India, Pakistan) as part of a comprehensive search for B. oleae throughout its range. Wild olives, Olea europaea ssp. cuspidata, were sparsely distributed and B. oleae-infested olives were scarce. Wild olives were most widespread in Pakistan where fly infestation reached 30%. Infested olives in southwestern China were rare, reaching only 5%. Flies were identified morphologically as B. oleae, the first record from China. No B. oleae were recovered from India or Nepal. Mitochondrial gene sequences from NADH dehydrogenase (ND1), cytochrome oxidase subunit 1 (COX1), and 16S rRNA were obtained from flies and compared with B. oleae sequences in GenBank. A single mitochondrial haplotype was found in Chinese flies. Chinese B. oleae represent a maternal lineage based on ND1 and COX1 that is highly divergent from other B. oleae. Phylogenetic analysis by maximum likelihood and Bayesian inference based on the concatenated dataset of B. oleae sequences with sequences of two close subcongeners, Bactrocera biguttula (Bezzi) and Bactrocera munroi White, and analysis of delineation of species boundaries using the genealogical sorting index, supported the idea that Chinese flies share recent common ancestry with B. oleae. Flies were parasitized by braconid wasps, Psyttalia ponerophaga (Silvestri) in Pakistan, and a Diachasmimorpha species in China. Our survey reinforces the possibility of finding new biocontrol agents of olive fruit fly in the Himalayan region.
Overuse of chemical insecticides such as organophosphates, pyrethroids, and endosulfan in managing notorious sap-sucking insect pests such as the melon aphid, Aphis gossypii Glover, resulted in insecticide resistance. To combat the above and bring out the novel pest control strategy, we implemented ribonucleic acid interference (RNAi), a reverse genetics tool in silencing the target genes. RNAi is a sequence-specific gene-silencing mechanism triggered by double-stranded ribonucleic acid (dsRNA). The efficiency of RNAi is reliant upon concentration of dsRNA, mode of delivery, gene targets, insect species, etc. The objective of the present study was to assess the extent of down-regulation by using two different concentrations of dsRNA specific to sodium channel (AgSCN) and ultraspiracle genes (AgUSP) (0.0625 and 0.125 mg/ml) with two time intervals (48 and 96 h) through oral delivery. The extent of declined gene expression and percentage mortality chronicled for sodium channel and USP is proportional to the dsRNA concentration. Thus, our study affirms the outlook in the development of RNAi which can form a potent species-specific tool in the management of insect pests such as A. gossypii.
Within the closed fig cavity packed with hundreds to thousands of fig wasps from multiple species, sensory structures on the antennae permit males to locate conspecific females for reproduction. When fig wasp females are seeking suitable figs for oviposition, antennal sensory structures perceive volatile compounds released from the target figs. In the present study, we investigated the sexual dimorphism of these important antennal sensillae by scanning electron microscopy. The antennal sensilla of Ceratosolen solmsi marchali Mayr, Philotrypesis pilosa Mayr, Philotrypesis sp., and Apocrypta bakeri Joseph in Ficus hispida displayed extreme dimorphism, with elaborated structures in females compared with degenerated structures in males. Sensilla coeloconica were absent in A. bakeri, but present in females of the other three species. Sensilla styloconica were present in both males and females of C. solmsi marchali, but were seen only in female of the other three species. Sensilla campaniformica, leaf-like sensilla, stylet-like sensilla, and bomb's hairs were seen only in female C. solmsi marchali. Sensilla short chaetica were only seen in Philotrypesis sp. The degeneration of male antennal sensilla of all studied fig wasps was important, but variable between species. In conclusion, sexual dimorphism of antennal sensilla of four species in Ficus hispida was consistent with their divergent biological and behavioral functions.
The spermathecae of Heteroptera exhibit great morphological variety. The characteristics of spermathecal morphology may contribute greatly toward the taxonomy and reproductive physiology of these insects. This study describes the spermathecal morphology of the agricultural pest, Leptoglossus zonatus (Dallas). The spermatheca of L. zonatus is distinguishable into three parts—the reservoir (distal portion), muscular duct (middle region), and enlarged duct (proximal end). The spherical reservoir has a cuticle-lined lumen, followed by a layer of flattened cells, below which lies another layer of cells with secretory characteristics. The muscular duct is characterized by a flange where the insertion of the muscle fibers is seen. The proximal duct is enlarged with a compartmentalized lumen. The morphological features of the spermatheca of L. zonatus differ from those described for other Heteroptera.
Trissolcus japonicus (Hymenoptera: Scelionidae) and Trissolcus plautiae are solitary endoparasitoids in eggs of stink bugs (Hemiptera: Pentatomidae). These two closely related parasitoids differ in their degree of host specificity. With the aid of scanning electron microscopy, we examined the external morphology, distribution, and abundance of the antennal sensilla of sexes of both species to gain insights into the olfactory mechanism in relation to host selection behavior. Seven types of sensilla were recorded in both species: basiconica, trichodea, grooved-peg, sickle-shaped, chaetica, papillary, and campaniformium sensilla. Sexual dimorphism of antennal structures occurred in both species. Male antennae possessed one more flagellomere and a larger number of olfactory sickle-shaped sensilla than female antennae, indicating that sensilla may be involved in mate or host location. There was a peg gland on the fifth antennomere of male antennae. Compared with males, females had a higher number of trichodea sensilla as well as papillary sensilla, which were not found in males. These sensilla might be involved in host recognition and acceptance during the drumming behavior of both species. No qualitative differences were recorded between the species in antennal structure, or sensilla types or topographical arrangement. However, the abundance of key sensilla was significantly different between species. T. plautiae females and males had larger numbers of trichodea sensilla than those of T. japonicus. T. japonicus females possessed fewer and larger sickle-shaped sensilla compared with T. plautiae females. These differences may provide a morphological basis for understanding the process of host habitat location and recognition in these parasitoids.
The exotic planthopper, Ricania speculum (Walker), was detected in 2014 in Liguria, Northern Italy, and recorded as first alert for Europe. This highly polyphagous species lays eggs on a wide range of host plants, including economically important crops. In this paper, we provide details on the egg-burster morphology and on the role it plays in the hatching process. Eggs are laid inside the tissues of young twigs or in the leaf midrib, leaving the anterior half and the micropylar area partially exposed. At hatching time, the mature embryo pierces through the eggshell with an egg-burster located on the mid-frontal region of the embryonic cuticle, never described so far in this species and in other Ricaniids. During the process of hatching, the embryonic cuticle splits over the head, progressively slipping downwards, and is finally released over the empty eggshell, with the egg-burster.
About 380 described species of Psylloidea occur on Eucalyptus in Australia. These show differences in diversification, feeding behavior, and apparent patterns of development. We analyzed the quality of nutrients used by three species of Aphalaridae belonging to different feeding guilds on three species of Eucalyptus. We evaluated the quantity and quality of total nonstructural carbohydrates (TNC), δ13C and δ15N isotope ratios, amino acids, and fatty acids. In general, TNC levels were greater in infested leaves than in uninfested leaves of the three species of Eucalyptus. TNC levels in the leaves of E. macrorhyncha F. Mueller ex Bentham were the highest and in E. globulus Labillardière the lowest. Total masses of amino acids and fatty acids were the greatest in the leaves of E. globulus infested by C. eucalypti (Maskell), followed by leaves of E. sideroxylon A. Cunningham ex. Woolls infested by the species of Glycaspis Taylor, and the lowest values were in the leaves of E. macrorhyncha infested by species of Synglycaspis Moore. In general, δ13C increased in C. eucalypti-infested leaves of E. globulus, Glycaspis sp. infested leaves of E. sideroxylon, and Synglycaspis sp. infested leaves of E. macrorhyncha. Nitrogen-isotope ratios (δ15N values) were not significantly different in infested and uninfested leaves. The free-living C. eucalypti stress E. globulus leaves more intensely by its group-feeding behavior, whereas the gall-inducing species of Synglycaspis stresses E. macrorhyncha leaves in such a way to elicit a response with a novel phenotypic expression, viz., the gall. The lerp-forming species of Glycaspis utilize nutrients, especially sugars, the excess of which is secreted to build their characteristic lerp.
Two new species of the pygmephoroid mites (Acari: Heterostigmata: Pygmephoroidea) are described and illustrated based on phoretic females found in northern forests of Iran: Propygmephorus crossi Katlav and Hajiqanbar sp. nov. (Pygmephoridae) phoretic on carabid beetles Pseudoophonus rufipes (DeGeer, 1774) and Pterostichus caspius (Menetries, 1832) (Coleoptera: Carabidae), and Archidispus irregularis Katlav and Hajiqanbar sp. nov. (Scutacaridae) associated with Bledius sp. (Coleoptera: Staphylinidae). The genus Propygmephorus Cross, 1974 is recorded from the eastern hemisphere for the first time and also redefined. The length of pretarsus IV in Archidispus varies among different species. Archidispus irregularis sp. nov. represents the most reduced pretarsus IV in the genus.
The phyline fauna of Australia has only recently been shown to be highly diverse, both at the species and the genus levels. Here, a new genus and four new species of Australian Phylinae (Hemiptera: Miridae) are described. The species of Restiophylus, n. gen., occur on two genera of the rush-like Restionaceae, Hypolaena Brown 1810 and Leptocarpus Brown 1810, and on one genus of the closely related Anarthriaceae, Lyginia Brown 1810. Habitus images, illustrations of male genitalia, scanning micrographs, an identification key, and distribution maps for the new species are provided as well as digital images and distribution maps for the hosts. Consistent with the geographic distribution patterns of many other Australian Phylinae, the four new species are restricted to the Mediterranean-type biome of Western Australia. A cladistic analysis based on 55 morphological characters, four ingroup taxa, and 31 outgroup taxa is presented, providing evidence for the monophyly of this new genus and its placement in the tribe Semiini, and potentially as sister to the subtribe Exocarpocorina.
The soil-feeding termite, Sinocapritermes mushae (Oshima & Maki), was described briefly in Japanese in 1919 and its type locality is Taiwan. S. mushae is the first found species of the genus, and all the other 15 congeners were described from China, and many of them were compared with S. mushae for species differentiation. However, the inconsistent interpretation of the original description of S. mushae soldier morphology occurred in Chinese literature. The winged imago of S. mushae was later described based on a single specimen collected in China, which is insufficient to represent the morphological variation and caused further confusion. To solve these problems, we re-describe and describe the soldier, winged imago, and worker enteric valve of S. mushae based on multiple colony samples collected from the type locality, Taiwan. Partial sequences of mitochondrial 16S gene confirmed that S. mushae is the only Sinocapritermes species found in Taiwan, but Taiwanese populations present high morphological variation. With the intraspecific variation of S. mushae, we demonstrated that most qualitative characters used for species differentiation among Chinese species are not valid. In addition, the morphometric data showed that the five species, Sinocapritermes sinensis Ping & Xu, Sinocapritermes songtaoensis He, Sinocapritermes tianmuensis Gao, Sinocapritermes yuannensis Ping & Xu, and Sinocapritermes xiai Gao & Lam, are not significantly different from S. mushae, and hence they are proposed as junior synonyms. This study indicates that the 15 exclusive Sinocapritermes spp. found in China need to be more thoroughly investigated, and a further revision of Sinocapritermes is necessary.
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