Non-reciprocal cross-incompatibility in Trichogramma deion

In non-reciprocal cross-incompatibility (NRCI), the crossing of a female of a strain A with a male of a strain B results in hybrid offspring, whereas the reciprocal cross produces few or no hybrids. Only females are of hybrid origin in Hymenoptera because they arise from fertilized eggs; males arise from unfertilized (haploid) eggs. Crosses between many strains of Trichogramma deion showed some degree of NRCI. Crosses between a T. deion culture collected in Seven Pines, California (SVP) with one from Marysville, California (MRY) showed an extreme form of NRCI in which practically no female offspring was produced when MRY females were crossed with SVP males. The reciprocal cross produced a close to normal proportion of female and male offspring. Detailed studied of this cross indicated that 1) the female offspring produced in the compatible interstrain cross were not the result of parthenogenesis but were true hybrids, 2) the incompatible interstrain cross did not produce female offspring because fertilized eggs died during development, 3) the death of these eggs could not be prevented by either antibiotic or temperature treatment, 4) cytoplasmically inherited factors causing NRCI could be discounted because backcrossed females with the genome of MRY and the cytoplasm of SVP, exhibit the NRCI relationship characteristic of their genome. Therefore the NRCI between these strains appears to be caused by a modification coded for by the nuclear genes of MRY that results in incompatibility when SVP sperm fertilizes MRY eggs. In addition the level of incompatibility in crosses between the SVP females and MRY males is temperature sensitive, the higher the rearing temperature the lower the level of compatibility.     

Factors influencing parasitism of Trichogramma dendrolimi on eggs of the Asian corn borer, Ostrinia furnacalis

Laboratory studies were made to determine the capacity of Trichogramma dendrolimi to parasitize eggs of Ostrinia furnacalis, as affected by the rearing host species, substrate of host eggs, host age, original locality of host populations, and cold storage of host eggs. Wasps reared from eggs of Antheraea pernyi showed parasitic capacity on eggs of O. furnacalis on average twice as high as that of the wasps reared from eggs of Corcyra cephalonica. When the age of O. furnacalis eggs at 26 °C increased from 0–6 h to 18–24 h, the proportion of wasps that successfully parasitized host eggs, the number of host eggs parasitized, and the rate of parasitization all decreased by >50%. The number of O. furnacalis eggs parasitized per female T. dendrolimi increased with the number of host eggs available, and reached 22.9 in a 24 h period. However, the parasitic capacity of female T. dendrolimi on eggs of O. furnacalis laid on plant leaves was similar to that of O. furnacalis eggs laid on wax paper. Levels of parasitism of O. furnacalis eggs from two widely separated localities, i.e. Changchun (43.50° N, 125.20° E) and Hangzhou (30.18° N, 120.07° E), were similar. Cold storage of O. furnacalis eggs at 4 °C for 5 days did not affect parasitization. Results obtained in this study indicate that although O. furnacalis is a less preferred and less suitable host than many other hosts, such as Dendrolimus punctatus, Actias selene ningpoane, Philosamia cynthia, A. pernyi, C. cephalonica, within the host-species range of T. dendrolimi, the parasitoid has the potential to achieve 50–60% or even higher rates of parasitization of O. furnacalis eggs in corn fields under suitable conditions, and could be used in the biological control of the pest.     

韩国新纪录属纹翅赤眼蜂属及一新种记述(膜翅目,赤眼蜂科)

首次报道了纹翅赤眼蜂属Lathromeris Foerster在韩国的分布,并记述了1个新种Lathromeris koreanica Hu,Lin et Kim与1个新纪录种Lathromeris germanica Girault.新种Lathromeris Koreanica与Lathromeris tumicalvata Lin相似,但新种缘前脉到痣脉下有明显的暗褐色斑块;缘前脉端部1/4处和缘脉基部1/9处有断痕.     

The smallest insects evolve anucleate neurons

The smallest insects are comparable in size to unicellular organisms. Thus, their size affects their structure not only at the organ level, but also at the cellular level. Here we report the first finding of animals with an almost entirely anucleate nervous system. Adults of the smallest flying insects of the parasitic wasp genus Megaphragma (Hymenoptera: Trichogrammatidae) have only 339-372 nuclei in the central nervous system, i.e., their ganglia, including the brain, consist almost exclusively of processes of neurons. In contrast, their pupae have ganglia more typical of other insects, with about 7400 nuclei in the central nervous system. During the final phases of pupal development, most neuronal cell bodies lyse. As adults, these insects have many fewer nucleated neurons, a small number of cell bodies in different stages of lysis, and about 7000 anucleate cells. Although most neurons lack nuclei, these insects exhibit many important behaviors, including flight and searching for hosts.     

Refinement of a cell line based artificial diet for rearing the parasitoid wasp, Trichogramma pretiosum

An artificial diet incorporating insect cells originally developed for Trichogramma australicum Girault (Hymenoptera: Trichogrammatidae) was successfully used to rear Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae). To refine the diet, individual components were removed. Chicken egg yolk and the insect cells were identified as the most important components for T. pretiosum development. Their removal resulted in few pupae and no adults. Removal of Grace’s insect medium, a common component of artificial diets, was found to markedly improve the development of T. pretiosum, producing 60% larva to pupa transition and 19% pupa to adult transition. There was no significant difference in T. pretiosum development on diets in which milk powder, malt powder or infant formula were interchanged, despite differences in nutrient composition. The use of yeast extract resulted in significantly higher survival to the adult stage when compared with yeast hydrolysate enzymatic and a combination of yeast extract and yeast hydrolysate enzymatic. Comparison of four antimicrobial agents showed the antibacterial agent Gentamycin and the antifungal agent Nystatin had the least detrimental effect on T. pretiosum development. The use of insect cell line diets has the potential to simplify artificial diet production and significantly reduce T. pretiosum production costs in Australia compared to diets using insect hemolymph or the use of natural or factitious hosts.     

尖角赤眼蜂属一新种及折脉宽翅赤眼蜂雌性记述(膜翅目:赤眼蜂科)

报道寄生拟隐脉叶蝉Sophonia spp.卵的尖角赤眼蜂属1新种,隐脉叶蝉赤眼蜂Hispidophila sophoniae sp.nov.,同时首次描述折脉宽翅赤眼蜂Ufens rimatus Linr的雌性特征,所有研究标本已制片,保存福建农林大学生物防治研究所。     

Effects of endosymbiotic Wolbachia on the diapause in Trichogramma hosts and effects of the diapause on Wolbachia

Abstract Used as an agent in biological control, Trichogramma which has been infected by endosymbiotic bacteria belonging to the genus Wolbachia and inducing the thelytokous mode of reproduction, increases rearing productivity in commercial insectaries. These insectaries can now make use of Trichogramma diapause to spread out and optimise their production. We therefore studied the effect of Wolbachia on the diapause in Trichogramma evanescens. The symbionts show no beneficial or harmful effect on the proportion of emergence in diapausing individuals or on their fecundity. Therefore, infected strains can easily be used in crop protection. On the other hand, low temperatures exert a slightly negative effect on Wolbachia, as detected from the proportion of females in the offspring of symbiotic diapausing females.     

Response of the egg parasitoid Trichogramma pretiosum to the sex pheromone of its host Heliothis zea

This paper presents results of olfactometer experiments with the egg parasitoid Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) and its host the corn earworm moth, Heliothis zea (Boddie) (Lepidoptera: Noctuidae). The sex pheromone of the host significantly reduced the total number of border crossings between odour fields in the olfactometer. Also, female parasitoids made significantly more visits to the calling moth odour field than to the opposite control field in the olfactometer. Further, the wasps spent significantly more time in the olfactometer field containing the sex pheromone released by calling virgin moths, than in control fields. If non-calling virgin moths were used as odour source, the response was reversed and wasps were repelled by the odour of the moths, and the numbers of visits were evenly distributed over the four flow fields. These results are discussed in the context of foraging ecology of egg parasitoids.

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Résumé Des expériences menées en olfactométrie avec le parasite oophage Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) et son hôte, Heliothis zea (Boddie) (Lepidoptera: Noctuidae) donnent les résultats suivants. La présence de la phéromone sexuelle de l'hôte réduit de façon significative le nombre de passages entre les champs odorisés. De mème, les parasites visitent plus fréquemment le champ qui dispense l'odeur de la femelle en appel que le champ témoin placé à l'opposé. Par ailleurs, le temps passé dans le champ qui contient la phéromone sexuelle émise par les femelles vierges en appel est significativement supérieur à la durée de visite des champs témoins. Si l'on utilise comme source d'odeur des femelles vierges qui ne sont pas en appel, la réponse est inversée, les parasites sont alors repoussés par l'odeur de ces papillons et le nombre de visites est distribué de façon aléatoire entre les quatre champs. Ces résultats sont discutés dans le contexte de l'écologie du comportement de recherche chez les parasites oophages.

     

The influence of previous host age on current host acceptance in Trichogramma

Trichogramma principium Sug. & Sor. females were sequentially offered two portions of the grain moth (Sitotroga cerealella Oliv.) eggs, either young (1-day old) or old (eggs that had developed 6 days at a temperature of 20 °C). The probability of host acceptance depended not only on current host age, but also on the age of the previously offered host. Particularly, Trichogramma females more often oviposited in old host eggs when previously offered young eggs (35–45% of Trichogramma females laid eggs) compared to females which were sequentially offered two portions of old eggs (15–20% of Trichogramma females laid eggs). In other words, parasitization by Trichogramma was stable even when transferred from young (preferred) to old (usually rejected) eggs. Dissections showed that refusing females had significantly more mature eggs than ovipositing females, independent of host age. Among ovipositing females, wasps provided with young hosts had fewer mature ovarial eggs than wasps provided with old hosts. Supposedly, Trichogramma females offered old hosts require a higher motivation to oviposit and have a correspondingly higher egg load than females offered young (preferred) hosts.