Effect of expected offspring survival probability on host selection in a solitary parasitoid

Optimal Foraging Theory predicts that parasitoid females should optimize their host selection to maximize their lifetime fitness gain and parasitize the most profitable hosts. In particular, in solitary parasitoids, females should avoid superparasitism, at least when sufficient unparasitized hosts are available. However, when unparasitized hosts are scarce, they should prefer, among already parasitized hosts, those that provide the best survival probability to their progeny, which depends on the age and the developmental stage of the first parasitoid. To test this hypothesis in a solitary ectoparasitoid, Pachycrepoideus vindemmiae Rondani (Hymenoptera: Pteromalidae), we first assessed the survival probability of a second parasitoid according to the time elapsed since initial parasitism. We then analyzed the female selection behavior in patches containing a mixture of hosts parasitized over various time intervals. Our results showed that the older the opponent larva was, the lower the survival probability of the second parasitoid was. However, when the first individual had reached the prepupal stage, both individuals could complete their development. At this stage, the survival probability of the second parasitoid was surprisingly high but such individuals were reduced in size. Our study also showed that host acceptance by females was strongly correlated with the survival probability of their progeny when the first parasitoid was from 0 to less than 10 days‐old. When the first parasitoid had reached the prepupal stage, females usually rejected these hosts, although the survival probability of the offspring was quite high. This discordance between female host selection behavior and progeny survival probability is discussed.     

Do grains whisper for help? Evidence for herbivore‐induced synomones in wheat grains

Thus far, the release of herbivore‐induced synomones (HIS) has almost exclusively been demonstrated in somatic plant tissue. Here we present evidence for the production of HIS from reproductive tissue, i.e., seeds. The study system consisted of wheat grains (Triticum aestivum L., Poaceae) infested by larvae of the granary weevil Sitophilus granarius L. (Coleoptera, Curculionidae), which in turn are attacked by the parasitic wasp Lariophagus distinguendus Förster (Hymenoptera, Pteromalidae). The use of potential chemical signals from the infested grain for host recognition of L. distinguendus was studied with weevil‐infested grains that had developed under a range of humidity conditions. Wasps always performed longer antennal drumming on infested than healthy grains, demonstrating that they were able to recognize infested grains under all humidity conditions. In grains developed at a high humidity (75% r.h.), host recognition is enabled by chemical signals arising from the host faeces which densely cover infested grains. However, in grains from a low humidity (45% r.h.) almost no faeces are present, indicating that other cues are used by the wasp. Control experiments revealed that these other cues are neither chemical signals from faeces contaminations, volatiles from faeces nor host larvae inside the grain, movement of host larvae, or moisture content of infested grains. Therefore, wasp recognition of infested grains in low humidity conditions is probably based on chemical signals from the grain itself that are induced by the feeding of granary weevil larva. Further experiments revealed that infested grains increase their viability when granary weevil larvae are killed by the idiobiont L. distinguendus. This justifies the categorisation of potential signals from the grain as HIS. To our knowledge, this is the only system where potential HIS in plant seeds have been studied. We discuss whether potential HIS are actively produced by infested grains or are a by‐product of grain metabolism.     

Associative Learning of Color by Males of the Parasitoid Wasp Nasonia vitripennis (Hymenoptera: Pteromalidae)

Males of the parasitoid wasp Nasonia vitripennis showed no innate preference for blue versus yellow or for green versus brown. They learned to associate color with mates, but their ability to do so depended on the color used and the strength of the reward. Specifically, males learned to associate brown or green with a reward of many virgin females. With fewer females, fewer training periods, or mated females as the reward, males still learned a preference for green but not for brown. Males did not learn to associate color with rewards of honey or water. Previous studies of color preference and associative learning in parasitoid wasps have focused almost entirely on females. This is the first demonstration of associative learning in response to visual cues by male parasitoid wasps.     

Parasitoids from Azores (Hymenoptera: Encyrtidae,Pteromalidae, Braconidae): potential use in integrated pest management against Ceratitis capitata (Diptera: Tephritidae)

Two hymenopterous parasitoids, Halticoptera patellana and Toxeumorpha nigricola, were recovered from Mediterranean fruit fly pupae on São Miguel Island, Azores. Both are new records for the Azores, and as Medfly parasitoids. Field-collected Tachinaephagus zealandicus was maintained on Medfly for 10 generations, but if it has potential as a biocontrol agent remains an open question.     

中国福建省金小蜂科三新种(膜翅目)(英文)

本文记述采自中国福建省的金小蜂三新种。短缘高角金小蜂Apsilocerabrevivenasp .nov .与Ap silocerabramleyiGraham相似 ,但本种缘脉短于后缘脉 ,颚眼距为复眼高的 1 /4。宽头短颊金小蜂Cleonymusgrandicepssp .nov .与CleonymuslaticornisWalker相似 ,但头宽为中胸宽的 1 .4倍 ,缘脉长为痣脉的 1 .9倍。圆唇宽胸金小蜂Norbanusarcuatussp .nov .唇基下缘中部呈明显的弧形的特征可以与该属其它种类相区别。模式标本均保存于中国科学院动物研究所动物标本馆     

X-ray computerized tomography as a new method for monitoring Amegilla holmesi nest structures, nesting behaviour, and adult female activity

Optimal foraging theory, specifically the marginal value theorem, predicts quicker leaving (shorter residence time) from poorer patches. One proximal mechanism for achieving the leaving is that exposure to lower-quality resources may trigger increased restlessness (proportion of time in locomotion). Which aspects of host quality, if any, affect restlessness was examined in females of the parasitoid wasp Nasonia vitripennis Walker (Hymenoptera: Pteromalidae). Females were individually exposed to a single host. Restlessness was greater both during and after exposure to a host, when the host was externally damaged vs. intact. Other aspects of host quality that affected restlessness were whether the host was parasitized and whether it was dead and unsuitable for offspring development. In contrast, the host's age and stage did not affect restlessness. Increased restlessness did not make females more willing to launch themselves across an inhospitable environment using their wings.     

Wolbachia in wasps parasitic on filth flies with emphasis on Spalangia cameroni

The house fly, Musca domestica L., and the stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae), are cosmopolitan pests parasitized by a guild of more than two dozen species of wasps. Several species of these wasps have been commercialized as biocontrol agents or are being studied for this purpose. Wolbachia bacteria are known to infect at least some of these wasps and are of interest because infections can dramatically affect insect reproduction. A survey in this parasitoid–fly system detected Wolbachia in 15 of 21 species of wasps and in three of nine species of flies parasitized by these wasps. Phylogenetic analyses using wsp gene sequences identified single isolate infections in most cases. Infections of two and four isolates were detected in Nasonia vitripennis (Walker) and Spalangia cameroni Perkins (Hymenoptera: Pteromalidae), respectively. Laboratory experiments showed infections in S. cameroni to cause an incomplete form of female‐mortality (FM) type cytoplasmic incompatibility (CI). Crosses between uninfected female and infected male partners (♀×♂^w) produced fewer progeny, which had a strong male‐biased sex ratio. Crosses between ♀×♂, ♀^w×♂^w, and ♀^w×♂ produced more progeny, which had a female‐biased sex ratio. Developmental times of progeny were increased when the paternal parent was infected with Wolbachia, regardless of whether the maternal parent was infected or whether offspring developed from fertilized eggs. This result may reflect the action of Wolbachia on components of the seminal fluid that then affect the development of offspring from inseminated females. It is hoped that future studies of Wolbachia in this guild will facilitate the rearing and application of these wasps as biocontrol agents of house fly and stable fly.     

A TAXONOMIC STUDY ON ASAPHES (HYMENOPTERA: PTEROMALIDAE) FROM CHINA,WITH DESCRIPTIONS OF FOUR NEW SPECIES*

Abstract This paper deals with six species of the pteromalid genus Asaphes from China, including four new species: Asaphes umbilicalis sp. nov., Asaphes globularis sp. nov., Asaphes siciformis sp. nov., and Asaphes oculi sp. nov. A key to the species based on the females is provided. The type specimens are deposited in the Zoological Museum, Institute of Zoology, Chinese Academy of Sciences, China.     

中国矩胸金小蜂属记述(膜翅目:金小蜂科)

本文记述了中国矩胸金小蜂属Syntonopus Walker一个新种S.fuscipes sp.nov.和四个新记录种。新种模式标本保存于中国科学院动物研究所。     

Predator‐parasitoid‐host interaction: biological control of Rhyzopertha dominica and Sitophilus oryzae by a combination of Xylocoris flavipes and Theocolax elegans in stored cereals

Post‐harvest management constraints are economically significant in Africa for a broad range of commodities, resulting in a substantial negative impact on food security and livelihoods. Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae) coexists with Sitophilus oryzae (L.) (Coleoptera: Dryophthoridae) – they infest stored cereal grains, especially in sub‐Saharan Africa, and cause significant losses in storage. Laboratory studies were carried out to determine the efficacy of Xylocoris flavipes (Reuter) (Hemiptera: Anthocoridae) and Theocolax elegans (Westwood) (Hymenoptera: Pteromalidae), alone or in combination, in suppressing populations of R. dominica and S. oryzae in stored rice and wheat grains. The weight loss and moisture of the infested grains were assessed, for the various combinations of the two pest insects and the two natural enemies. In rice there was a synergistic effect of the combined release of T. elegans and X. flavipes against both R. dominica and S. oryzae compared to the effect of one natural enemy alone. With the combined release, only 2% F₁ progeny of the pest beetles emerged compared to the untreated control (100%), whereas 3.5 and 6% emerged when X. flavipes and T. elegans, respectively, were released alone. When the two natural enemies were released in combination, 0.4% R. dominica F₁ progeny emerged, compared to 1.6% with X. flavipes or T. elegans alone. In the combined release only 0.3% S. oryzae F₁ progeny emerged, whereas 65% emerged with X. flavipes alone and 41% with T. elegans alone. No synergistic effect of the combined release of the two natural enemies was detected in wheat. In stored rice, the lowest percentage of weight loss (44%) was found when both natural enemies and both beetle species were present. We conclude that the combination of the predator and the parasitoid should be recommended when R. domininca and S. oryzae coexist and feed on stored cereals, especially rice.