No description available.

No description available.

No description available.

In this paper, 48 ichneumonid species of 14 genera, two tribes of the subfamily Pimplinae were listed on the basis of material collected during the time from 2003 to 2011 in four provinces from the Central Highlands of Vietnam and a lesser degree of previous records. Among 48 aforemention pimpline no less than 16 species were described recently as new for science. The diversity of topography and vegetation types resulted in the high level of species richness and new discoveries of the region. / Bài báo này giới thiệu danh sách 48 loài ong cự thuộc 14 giống, 2 tộc của phân họ Pimplinae dựa trên việc phân tích các mẫu vật thu tại Tây Nguyên trong thời gian từ năm 2003–2011 và một số ít loài dựa trên các ghi nhận trước đây. Trong số đó, 16 loài mới được mô tả trong thời gian 5 năm trở lại đây. Sự đa dạng về địa hình và các kiểu thảm thực vật khác nhau đã tạo nên tính đa dạng thành phần loài và các phát hiện mới của ong cự ở khu vực Tây Nguyên đầy tiềm năng này.

Although parasitoid wasps have shown promise as model systems for studying life history evolution, empirical studies of certain traits in these small insects have proven difficult. In this dissertation, two "black boxes" in the life histories of female parasitoids are examined: (1) oosorption, and (2) dispersal by flight.I first demonstrate that a short-lived species with high early reproductive investment (Eretmocerus eremicus) resorbs eggs, which runs counter to the notion that the time costs of oosorption are prohibitive to such wasps. Instead, it appears that the resorption mechanism in E. eremicus is capable of both decreasing costs and increasing nutritional benefits of oosorption relative to that of other parasitoid species. In addition, a literature review reveals four functional hypotheses for parasitoid oosorption: (1) age-related egg apoptosis, (2) conservation of ovarian capacity, and (3) nutrient allocation to either longevity or future oogenesis. As none of these can be rejected, I propose several avenues of future research: 1) refinement of physiological techniques to measure nutrient traffic into and out of eggs, 2) morphological phylogenetic studies of oosorption mechanisms, 3) development of lifetime nutrient budgets for parasitoids with different reproductive life histories, 4) examination of decay rates of oocytes with different yolk types, and 5) increased study of ovarian dynamics in pro-ovigenic parasitoids.Next, I describe results from a vertical flight chamber study designed to test hypotheses regarding the correlation between pre-oviposition dispersal and reproductive effort in parasitoid wasps. This experiment was conducted on 1-d-old female whitefly parasitoids from five species in two genera. The two Eretmocerus spp. showed a higher flight propensity than the three Encarsia spp. This may be, in part, due to a more time limited life history in the former. Within species, egg load did not correlate well with flight propensity for all species examined. Finally, among individuals of Er. eremicus, the relationship between effective flight distance and egg load appears to be context dependent, as data consistent with both positive and negative correlations were collected. Correlational changes between flight distance and egg load may be due to variation in biotic (female longevity) or abiotic (temperature, relative humidity) factors.

Insects have become increasingly resistant to chemical control methods, while at the same time public awareness of the harmful effects of synthetic pesticides has increased. The search for more environmentally 'friendly' means of pest suppression is gaining momentum and biological control (the use of natural enemies to reduce populations of noxious organisms) has become an increasingly sought-after option. Despite an increase in the establishment rate of insect natural enemies, classical biological control of arthropods is currently no more successful than it was one hundred years ago. Ecological theory relevant to population biology, food webs and diversity provides insight into how biological control agents can be made more effective, yet this theory has often been absent from the biological control literature. Examples of the use of ecological concepts (including intraguild predation, life-history omnivory and resource subsidies) in practical biological control are reviewed, and aspects of theory not yet considered in this context are discussed. Cereals are important as primary food crops, globally and within New Zealand. Possibly the greatest amount of damage sustained by cereal crops in New Zealand is caused by aphids and chemical control of these pests is very expensive relative to biological control. This thesis examines how biological control of the rose-grain aphid Metopolophium dirhodum (Walker) (Hemiptera: Aphidiidae) by the koinobiont, synovigenic endoparasitoid Aphidius rhopalosiphi De Stefani-Perez (Hymenoptera: Aphidiidae) can be enhanced by floral resource subsidies. The mechanisms underlying this enhancement were determined in a series of laboratory experiments and then tested in laboratory microcosms and in the field. Sugar resources significantly increased longevity and egg load in A. rhopalosiphi and another species of aphidiid, Diaeretiella rapae McIntosh. Pollen had no significant effect on longevity or egg load in these species. These results are discussed in terms of the effects of resource subsidies on egg- versus time-limitation. Laboratory microcosm experiments tested whether the mechanisms of increased potential fecundity via enhanced egg load and longevity translate into increased rates of parasitism (i.e., realised fecundity). Only treatments receiving sugar showed increased reproductive success. The presence of flowering buckwheat Fagopyrum esculentum Moench (c.v. Kitawase) (Polygonaceae) plants caused a slight, non-significant increase in rates of parasitism. Field surveys of natural aphid populations in a wheat Triticum aestivum (L.) (c.v. Otane) (Gramineae) field showed that proximity to floral buckwheat patches, distance to the nearest edge or the leeward end of the field were not significantly correlated with rates of parasitism. These variables were significantly correlated with aphid density in some surveys. Rates of parasitism were not correlated with aphid density. When aphid population density was controlled by experimental placement of aphids, proximity to floral resource patches significantly affected rates of parasitism. Parasitism rates were highest at the edges of buckwheat patches and declined exponentially with distance, eventually reaching zero beyond 14 m. Lower levels of parasitism were observed within the floral patches than at their edges. This phenomenon is compatible with the concept of spatio-temporal partitioning between parasitoid feeding and host-searching behaviours. Potential costs (increased predation risk, opportunity costs) and benefits (increased fecundity and longevity) associated with floral feeding by parasitoids, and temporal variation in these factors, are discussed. It is concluded that resource subsidies are not only effective in the practical enhancement of the efficacy of a specific biological control agent, but their use is based on a sound foundation in ecological theory that allows extension of these principles across taxa.

Physiological factors that might influence ecological dynamics were investigated to better explain the biology of Bemisia tabaci in the desert southwest. Trehalulose, a unique disaccharide only found in unusually large quantities in B. tabaci honeydew, was shown not to be different from sucrose in promoting longevity in honeydew-consuming parasitoids, indicating this insect-modified sugar does not affect the nutritional quality of aleyrodid excreta. Trehalulose is not believed to function as a feeding deterrent to natural enemies. Experiments were designed to examine the effect of temperature on sorbitol and trehalulose production by the whitefly. High performance liquid chromatography analysis of honeydew and whole body extractions revealed a negative relationship between amounts of trehalulose in the honeydew and sorbitol accumulation in the whitefly body, linking these two molecules as important to the nutritional ecology of whiteflies. In another experiment to better understand the dispersal of whiteflies across the landscape, studies of flight over multiple days were conducted to describe the role of prior flight experience on dispersal and migratory flight. Flight performance traits were measured over multiple days of flight to compare two groups of B. tabaci, those trapped moving outside of planted fields with those collected within fields. Trap-caught individuals exhibited flights of significantly shorter duration in a vertical flight chamber. Flights determined to have characteristics of migratory behaviors were initially of longer duration for trap-captured whiteflies than their field-collected counterparts. Over the context of multiple days, however, their longer flights were followed by much shorter flights on subsequent days. Although many insects from both groups were capable of movement on multiple days, almost all of these flights were of a foraging nature. Foraging flights of short duration would likely not add to dispersal distances, thereby limiting whiteflies to their originating patch.

No description available.

Parasitoid insects face the fundamental problem of finding a suitable host in environments filled with competing stimuli. Many are deft sensors of olfactory cues emitted by other insects and the plants they live on, and use these cues to find hosts. Using olfactory cues from host-plants is effective because plants release volatile organic compounds (VOCs), in response to herbivory or oviposition, that contain information about the presence of hosts. However, plant-produced cues can also be misleading because they are influenced by a variety of stimuli (abiotic variation, infection and multiple sources of induction via herbivory or oviposition). Flexible behavior is one strategy that parasitoids may use to cope with variation in olfactory cues. We examine the innate and learned responses of a natural population of wasp egg parasitoids (Trichogramma deion and Trichogramma sathon) using a series of laboratory and field Y-olfactometer experiments. Wasps typically attack eggs of the hawkmoth Manduca sexta and Manduca quinquemaculata on native Datura wrightii plants in the southwestern United States. We show that Trichogramma wasps responded innately to VOCs produced by D. wrightii and could distinguish plants recently attacked by M. sexta from non-attacked plants. Furthermore, adult Trichogramma wasps were able to learn components of the VOC blend given off by D. wrightii, though they did not learn during exposure as pupae. By further exploring the behavioral ecology of a natural population of Trichogramma, we gain greater insight into how egg parasitoids function in tri-trophic systems.

Thesis (doctoral)--Universität, Bonn, 1999.