补充非寄主源食物显著提高万氏潜蝇姬小蜂孤雌产雌品系对美洲斑潜蝇的控害潜力

[目的]万氏潜蝇姬小蜂Diglyphus wani是潜叶蝇类害虫的重要寄生蜂,可以孤雌产雌生殖,仅产生雌性后代,具有潜在的生防应用价值.该寄生蜂为寄主取食型寄生蜂,自然条件下不仅可取食非寄主源食物,也可直接取食寄主幼虫.本研究旨在探究补充非寄主源食物对其生防效果的影响,从而有效指导其大规模饲养和田间应用.[方法]以万氏...     

Life history and life table of the host-feeding parasitoid <Emphasis Type="Italic">Hemiptarsenus varicornis</Emphasis> (Hymenoptera: Eulophidae)

Hemiptarsenus varicornis (Girault), a destructive host-feeding wasp, is an important biocontrol agent/larval ectoparasitoid of agromyzid leafminers worldwide. In the present study, the life history and life table of H. varicornis reared with Liriomyza trifolii (Burgess) were studied at a constant 27 °C. The developmental durations of female and male eggs, larvae, prepupae, pupae and total immature wasps were 1.00 and 1.00, 2.57 and 2.62, 0.45 and 0.37, 3.88 and 3.52, and 7.90 and 7.52 days, respectively. This wasp showed three types of host-killing behavior: reproductive parasitization (parasitism), non-reproductive host feeding (host feeding), and host stinging without oviposition or feeding (host stinging), resulting in 133.9, 303.8, and 84.2, respectively, killed host larvae. We confirm that H. varicornis is a strong synovigenic parasitoid, with an ovigeny index of 0.003. The number of host-feeding events was strongly correlated with parasitism, host-stinging events, longevity and total host mortality. The intrinsic rate of increase, the finite rate of increase, the net reproductive rate, the gross reproduction rate, and the mean length of a generation of H. varicornis were 0.3011/day, 1.3624/day, 66.22 offspring/individual, 168.33 offspring/individual, and 13.56 days, respectively. These results could contribute to a better understanding of the biocontrol efficiency of this destructive host feeder.     

补充非寄主食物对芙新姬小蜂和潜蝇姬小蜂控害行为权衡的影响

芙新姬小蜂和潜蝇姬小蜂均为强卵育型(synovigenic)寄生蜂,成虫具有产卵寄生致死、寄主取食致死和寄主叮蛰直接致死3种寄主致死行为。为了明确成虫补充非寄主食物营养对2种姬小蜂控害潜力/控害行为的影响,本文比较研究了分别提供寄主食物和寄主食物+非寄主食物(10%葡萄糖)条件下的2种姬小蜂在初羽化前期(前6 d)内对美洲斑潜蝇幼虫的致死行为的影响。结果显示:在仅提供寄主食物时,芙新姬小蜂的寄生、取食和总体致死量均显著的高于潜蝇姬小蜂,但是直接致死能力却弱于后者;补充非寄主食物和仅提供寄主食物处理相比,两种寄生蜂的寄生量,取食量和总致死量均呈下降趋势。该研究显示:在初羽化前期,取食寄主食物的雌蜂比取食寄主食物+葡萄糖的雌蜂具有更强的致死能力。     

Adult feeding and lifetime reproductive success in the parasitoid Aphytis melinus

The diet of adult females of the parasitoid Aphytis melinus DeBach (Hymenoptera: Aphelinidae) includes host insects and sugar-rich foods such as nectar and honeydew. We compared the contributions of host feeding to longevity and fecundity in A. melinus females in the presence and in the absence of honey meals. First, we assessed the longevity of females that were not allowed to oviposit. While the longevity of females fed honey was significantly increased by host feeding (median ages were 30.5 days for host-fed females and 17 days for females not allowed to host feed), the lifespan of parasitoids not fed honey did not exceed 3 days for any individual and there was no effect of host feeding on longevity in this group. In the second set of experiments, we assessed the fecundity and longevity of females allowed to oviposit. We conducted two experiments, one in which honey was continuously available, and one in which honey was not available. In both experiments, daily observations were made of females that were either allowed to host feed or manually prevented from host feeding. In the presence of honey, host feeding significantly increased both fecundity and longevity, and in the absence of honey, parasitoids died within 2 days and host feeding had no significant effect on either fecundity or longevity. The lifetime fecundity of females fed honey but not hosts exceeded the initial egg complement by 60% on average. Approximately one host per day was used for host feeding whether honey was supplied or not, and each host-feeding meal contributed approximately 3.9 eggs to the lifetime fecundity of honey-fed females. In the last experiment, we compared the rate of egg resorption over a 36-h period in A. melinus females that were deprived of hosts and either fed honey or starved. While no egg resorption was detected in honey-fed females over this time period, starved females resorbed approximately 9 eggs. Thus, the availability of a sugar-rich food interacts strongly with host feeding in influencing longevity and fecundity and has a strong direct effect on egg resorption.     

Food-deprived host-feeding parasitoids kill more pest insects

Some parasitoids not only parasitize their hosts but also destructively feed on them which could result in host mortality. We hypothesized that host-feeding parasitoids that are food-deprived before being released for biological control would destructively feed on more hosts, and an optimal duration of food deprivation of parasitoids would enhance host feeding without negatively affecting parasitism. We investigated the effects of food-deprivation durations (0, 3, 6, 10, 24 h and 20% honey solution offered), before being released, on the host mortality and parasitism by a destructive host-feeding parasitoid of whitefly nymphs, Encarsia sophia (Girault & Dodd) (Hymenoptera: Aphelinidae). In another experiment, we compared host feeding, parasitization and longevity throughout the lifespan between food-deprived and non-food-deprived parasitoids. Using fourth-instar Bemisia tabaci B biotype as the host, the responses of E. sophia differed significantly with the durations of food deprivation before they were exposed to their hosts. E. sophia adults food-deprived for 6 h killed more hosts through feeding than those that were food-deprived for 0, 3, 10 and 24 h or those that were fed with honey solution. Moreover, parasitoids that were food-deprived for 6 h parasitized more hosts than those held for other durations of food deprivation. Similar results on host-feeding were found when third-instar whitefly nymphs were used. We confirmed that E. sophia food-deprived for 6 h not only killed more whiteflies through host feeding, but also lived significantly longer and parasitized more hosts than the non-food-deprived ones throughout their lifespan. Our results could be extended to improve the effectiveness of augmentative biological control of pests through improved host feeding and parasitizing capacity by starving the parasitoids for a certain period of time before they will be used.     

Host-feeding and oviposition strategies of parasitoids in relation to host stage

Until now, mathematical models of parasitoid-host interactions have not incorporated the tendency for destructively host-feeding parasitoids to partition their feeding and oviposition behaviour in relation to different host stages. A literature survey reveals a trend for female parasitoids to feed preferentially or exclusively on earlier host stages and to oviposit preferentially or exclusively in/or later ones. We explore the relative advantages to host-feeding parasitoids of a number of possible host stage selection strategies. We develop hypotheses, formalizing and testing them using modifications to our earlier simulation model of host-feeding strategies (Jervis and Kidd, 1986). We conclude from our modelling that the advantage to be gained from feeding on early host stages and ovipositing in late ones is likely to be associated with: 1) reduced handling times when feeding on early stage hosts; 2) reduced wastage of progeny from mortality factors other than host-feeding by the parent parasitoid, achieved by confining oviposition to late host stages; and 3) reduced probability of progeny mortality resulting from the parent's host-feeding activities.     

温度对芙新姬小蜂孤雌产雌品系成虫控制斑潜蝇的潜力的影响

【目的】芙新姬小蜂Neochrysocharis formosa是潜叶蝇类害虫的优势寄生蜂。该寄生蜂具有两性生殖和孤雌产雌生殖两种繁殖模式,其孤雌产雌品系可在低密度下快速建立种群,无需饲养雄蜂,具有种群繁育成本低,生防应用潜力突出等优点。本研究旨在明确环境温度对芙新姬小蜂孤雌产雌品系控害潜力的影响,为该蜂的低成本规模化繁育、田间释放等应用实践提供参考。【方法】在室内以美洲斑潜 蝇Liriomyza sativae 2龄末至3龄初幼虫为寄主,统计4个温度(22, 26, 30和34℃)下芙新姬小蜂孤雌产雌品系雌成虫的取食致死寄主数、寄生致死寄主数、叮蛰致死寄主数、总致死寄主数、日均致死寄主数和成蜂寿命等生活史和控害参数。【结果】随温度升高,芙新姬小蜂孤雌产雌品系雌成虫对美洲斑潜蝇幼虫取食致死寄主数、寄生致死寄主数、叮蛰致死寄主数、总致死寄主数和日均总致死寄主数呈现先增加后降低的趋势,其中取食致死寄主数、寄生致死寄主数和叮蛰致死寄主数在30℃下最高,分别为236.1, 69.2和49.7头;在34℃下最低,分别为115.2, 19.8和21.6头。总致死寄主数在26℃(282.4头)和30℃(355.0头)下显著高于22℃(194.5头)和34℃下(156.5头);日均总致死寄主数在30℃下最高(25.5头)。此外,随着环境温度升高,芙新姬小蜂孤雌产雌品系雌成虫的寿命逐渐缩短,在22℃下最长(16.9 d),在34℃下最短(7.2 d)。【结论】尽管高温缩短了芙新姬小蜂孤雌产雌品系成虫的寿命,但其在30℃下控害能力较强,说明芙新姬小蜂孤雌产雌品系成虫可在30℃高温条件下对耐高温的斑潜蝇如美洲斑潜蝇发挥其控害潜力。     

营养改变对潜蝇姬小蜂寄生行为和寄主取食行为的影响

为了研究营养状态对卵育型寄生蜂潜蝇姬小蜂Diglyphus isaea (Walker)雌蜂的寄主取食行为和产卵寄生行为及其二者行为权衡的影响, 在培养皿条件下, 比较了饥饿、加蜂蜜水和不加蜂蜜水3种营养状态的潜蝇姬小蜂雌蜂对美洲斑潜蝇Liriomyza sativae Blanchard各龄幼虫（低、中、高）的寄生、取食及致死能力。结果表明: 非选择条件下, 3种营养状态寄生蜂对高龄幼虫均具有较高的寄生率, 对中龄幼虫具有较高的取食率, 致死率和致死量之间存在显著性差异。3种状态的寄生蜂对低龄幼虫均没有表现出致死能力。有选择条件下, 饥饿状态的寄生蜂对寄主的寄生率最低（5.0%±1.6%）, 取食率最高（16.0%±2.9%）, 特别是对高龄幼虫的取食率占到了整个寄主食物取食率的91.9%; 加蜂蜜水状态下, 寄生蜂对寄主有最低的取食率（8.3%±0.9%）和致死率（17.7%±1.1%）; 不加蜂蜜水状态下, 寄生蜂对寄主有最高的寄生率（13.3%±1.1%）和致死率（28.4%±1.8%）。综合分析发现, 取食寄主的雌蜂比取食蜂蜜水的雌蜂具有更强的致死能力和活动能力。     

潜蝇姬小蜂属寄生蜂对潜叶蝇的控害特性及应用

潜蝇姬小蜂属Diglyphus寄生蜂是潜叶蝇类害虫的重要天敌。本文对其种类、 分布、 田间发生和优势度、 优势种的控害特性和生态适应性, 以及优势种的人工繁殖和田间应用等进行总结和展望, 以期为更好地应用该属寄生蜂防控我国潜叶蝇的研究和应用提供指导。迄今已鉴定该属寄生蜂36种, 全为抑性外寄生蜂, 其中针对豌豆潜蝇姬小蜂D. isaea、 贝氏潜蝇姬小蜂D. begini和中带潜蝇姬小蜂D. intermedius的研究较多。雌蜂不仅可通过繁殖型的寄生方式而且还可通过非繁殖型方式（取食寄主和产卵器插入直接杀死）致死寄主。雌蜂偏好寄生大个体寄主和取食相对较小个体的寄主, 且雌蜂对寄主幼虫的偏好具有“寄主大小依赖型性别分配”现象（host-size-dependent sex allocation）。从温度适应范围和控害潜力首推为豌豆潜蝇姬小蜂。优势种的规模饲养技术已经被研发并得到了较广泛的田间应用。未来研究可主要集中于： （1）加强优势种尤其是温度适应范围广或较为耐热的种群或地理品系的研究, 以增加对三叶草斑潜蝇Liriomyza trifolii和美洲斑潜蝇L. sativae的控效; （2）加强雌蜂寄主取食行为特性及其生理机制的研究, 以更高效利用; （3）因地制宜研发规模化饲养技术和释放技术; （4）加强潜蝇姬小蜂同其他潜叶蝇寄生蜂的协同控害及竞争共存机制的研究, 已提升对潜叶蝇的生防控制效果。     

Shifting preference between oviposition vs. host-feeding under changing host densities in two aphelinid parasitoids

Destructive host-feeding is common in hymenopteran parasitoids. Such feeding may be restricted to host stages not preferred for oviposition. However, whether this is a fixed strategy or can vary according to resource levels or parasitoid needs is less clear. We tested the trade-off between host feeding and oviposition on two whitefly parasitoids under varying host densities. Females of two aphelinid parasitoids, Eretmocerus hayati and Encarsia sophia were exposed to nine different densities of their whitefly host, Bemisia tabaci, in single-instar tests to identify their functional response. Mixed-instar host choice tests were also conducted by exposing whiteflies at four densities to the parasitoids. We hypothesized that the parasitoid females can detect different host densities, and decide on oviposition vs. host-feeding accordingly. The results showed that both Er. hayati and En. sophia females tended to increase both oviposition and host-feeding with increased host density within a certain range. Oviposition reached a plateau at lower host density than host-feeding in Er. hayati, while En. sophia reached its oviposition plateau at higher densities. At low densities, Er. hayati parasitized most on first and second (the optimal ones), and fed most on third nymphal instars (the suboptimal one) of the whitefly host as theory predicts, while at high densities, both parasitism and host-feeding occurred on first and second instars which are preferred for oviposition. En. sophia parasitized most on third and fourth (the optimal ones), while fed on first instars (the suboptimal one) at low densities, and utilized third and fourth instars for both at high densities. In conclusion, oviposition vs. host-feeding strategy of parasitoid females was found to vary at different host densities. The balance between reserving optimal hosts for oviposition or using them for host-feeding depended on parasitoid life history and the availability of host resources.     

Contrasting patterns of ovarian development and oogenesis in two sympatric host-feeding parasitoids,Diglyphus isaea and Neochrysocharis formosa (Hymenoptera: Eulophidae)

Diglyphus isaea (Walker) and Neochrysocharis formosa (Westwood) (Hymenoptera: Eulophidae) are common idiobiont parasitoids of leafminers attacking vegetable crops. They exhibit differing levels of synovigeny, and host feeding enhances their fecundity and longevity. The reproductive systems of these two parasitoids are typical of hymenopteran eulophids, consisting of two ovaries, each usually comprising three polytrophic meroistic ovarioles. Diglyphus isaea possesses two obvious oviduct accessory glands, which are absent in N. formosa. Both parasitoids underwent oosorption when starved, while feeding on host larvae promoted oogenesis and egg maturation. In both, oogenesis and vitellogenesis commenced on the first day of the pupal stage rather than after eclosion. Formation of ovarioles in D. isaea commenced 1 day earlier than in N. formosa. Mature eggs were rarely observed in ovaries of newly emerged D. isaea, but usually a few were present in N. formosa. When hosts (second–third instar Liriomyza sativae larvae) were provided, the number of mature eggs in D. isaea ovaries initially increased and then stabilized, while in N. formosa, the number first increased and then decreased. Diglyphus isaea had fewer but larger eggs than N. formosa did. Thus, synovigenic divergence begins at the pupal stage and may result in different life-history traits of adults.     

Dynamic host-feeding and oviposition behavior of an aphid parasitoid <Emphasis Type="Italic">Aphelinus asychis</Emphasis>

In order to maximize the lifetime reproductive success of parasitoids, they should be induced to dynamically accept individual hosts that have different suitability for oviposition. Parasitoids tend to exhibit higher host-selective behavior when their egg load is limited, and are less selective if they are facing time constraints. Here, we evaluated the effects of parasitoid age on egg load, fecundity and host instar preference of a honey-fed aphid parasitoid, Aphelinus asychis Walker (Hymenoptera: Aphelinidae). Host selective experiment was conducted to measure host-preference of honey-fed A. asychis females at different ages, using the second and fourth instars of the green peach aphid Myzus persicae as their hosts. The results showed that the choice of host-instar for oviposition was significantly influenced by the parasitoid age. Honey-fed parasitoids in the age groups of 1, 5, 10 and 20 days tended to parasitize predominantly second-instar aphids, whereas 15-days old parasitoids showed no significant preference of host instars. On the other hand, host-feeding preference was not affected by parasitoid age. Parasitoid females of all ages preferred younger aphids to older aphids. This result could help evaluate the effectiveness of A. asychis for biological control of M. persicae when they encountered mixed-instar aphids in the field. In addition, the results might be helpful in assessing the host killing effects of other host-feeding parasitoids.     

Importance of host feeding for parasitoids that attack honeydew-producing hosts

Insect parasitoids lay their eggs in arthropods. Some parasitoid species not only use their arthropod host for oviposition but also for feeding. Host feeding provides nutrients to the adult female parasitoid. However, in many species, host feeding destroys an opportunity to oviposit. For parasitoids that attack Homoptera, honeydew is a nutrient‐rich alternative that can be directly imbibed from the host anus without injuring the host. A recent study showed that feeding on host‐derived honeydew can be an advantageous alternative in terms of egg quantity and longevity. Here we explore the conditions under which destructive host feeding can provide an advantage over feeding on honeydew. For 5 days, Encarsia formosa Gahan (Hymenoptera: Aphelinidae) parasitoids were allowed daily up to 3 h to oviposit until host feeding was attempted. Host feedings were either prevented or allowed and parasitoids had ad libitum access to honeydew between foraging bouts. Even in the presence of honeydew, parasitoids allowed to host feed laid more eggs per hour of foraging per host‐feeding attempt than parasitoids that were prevented from host feeding. The higher egg‐laying rate was not compromised by survival or by change in egg volume over time. In conclusion, host feeding can provide an advantage over feeding on honeydew. This applies most likely under conditions of high host density or low extrinsic mortality of adult parasitoids, when alternative food sources cannot supply enough nutrients to prevent egg limitation. We discuss how to integrate ecological and physiological studies on host‐feeding behavior     

The parasitoid of a fruit moth caterpillar utilizes fruit components as nutrient source to increase its longevity and fertility

Longevity and fecundity of female wasps are two decisive factors for the effectiveness of parasitoid species as biological control agents. Accessibility and suitability of nutrient sources determine parasitoid survival and reproduction. Host, nectar and honeydew feeding are frequent adult parasitoid behaviors to cover nutritional needs. Here we postulate that especially parasitoid species of endophytic herbivores might use plant tissue as a nutrient source that becomes accessible upon herbivory. We investigated the influence of plant consumption and host feeding on longevity and fecundity of Hyssopus pallidus, a gregarious ecto-parasitoid of caterpillars of the codling moth that feed inside apple fruits. Longevity of unmated and mated ovipositing female parasitoids was highest in treatments with fruit pulp. While longevity in this treatment was not significantly different from that with honey, it was significantly higher than in treatments without food, with water or with a host alone.Reproduction was significantly increased by these sugar-rich nutrient sources compared to the control with a host alone. In contrast, host feeding did not yield any significant contribution to longevity and fecundity in a series of bioassays with different host–parasitoid ratios and with differently aged and sized hosts, compared to controls without food.We conclude that in this synovigenic species host feeding does not contribute to longevity and fecundity, but females can increase survival and reproduction in the field relying solely on the plant tissue damaged by their host caterpillar.     

A simulation study of population interaction between the greenhouse whitefly,Trialeurodes vaporariorum Westwood (Homoptera: Aleyrodidae) and the parasitoidEncarsia formosa Gahan (Hymenoptera: Aphelinidae) II. Simulation analysis of population dynamics and strategy of biological control

Simulation studies were performed to analyze factors affecting the population dynamics of the system with the greenhouse whitefly (Trialeurodes vaporariorumWestwood ) and the parasitoid Encarsia formosaGahan and to develop strategies for the introduction of E. formosa. The reduction of parasitization efficiency with an increase in parasitoid density promotes the stability of the system, which coincides with the prediction from current theory. The stability of the system is also shown to be promoted by the effect of host feeding. The population levels of the system are remarkably suppressed with an increase in searching efficiency and a decrease in host oviposition. The control effect of the parasitoids is enhanced when the number of parasitoids is divided among many introductions. An optimal time, an optimal density ratio of parasitoids to hosts and optimal densities of hosts and parasitoids exist in the introduction programme of parasitoids.     

寄生蜂取食寄主特性及其在害虫生物防治中的作用

许多寄生性天敌昆虫的雌虫不仅寄生寄主, 而且还能取食寄主。在卵育型（synovigenic）寄生蜂类群中, 取食寄主行为是较为普遍的现象。本文综合近20年相关研究进展, 从寄生蜂类群、取食类型、生态学意义及影响因子等方面对寄生蜂的取食寄主行为进行了归纳总结。寄生蜂通过取食不仅可以杀死寄主, 直接起到控制害虫种群数量的作用, 还能通过取食策略为卵的成熟和再生提供营养来源, 对延长雌虫的寿命也有一定的帮助。对取食寄主行为的了解可为筛选优势寄生性天敌种类、评估寄生蜂在害虫生物防治中的作用提供重要信息。     

Influence of egg load and host size on host-feeding behaviour of the parasitoid Aphytis lingnanensis

Abstract.

• 1 Direct behavioural assays were used to investigate the influences of host size and parasitoid egg load on the decision to host feed versus oviposit made by the parasitoid Aphytis lingnanensis Compere. Egg load was manipulated without concurrent influences on the history of host contact by exploiting size-related variation in fecundity and by holding parasitoids at different temperatures to vary the rate of oocyte maturation.
• 2 Host feeding comprised a series of feeding bouts, separated by renewed probing of the scale insect body. Successive feeding bouts were progressively shorter, suggesting that hosts represent ‘patches’ yielding resources at a decelerating rate.
• 3 Parasitoids were significantly more likely to host feed on smaller hosts and oviposit on larger hosts.
• 4 Neither egg load nor the treatment variables (parasitoid size and holding temperature) exerted significant influences on the decision to host feed versus oviposit on second instar (low quality) hosts.
• 5 The failure to observe an effect of egg load on host-feeding decisions was not simply a reflection of the parasitoids being entirely insensitive to egg load; significant effects of egg load on parasitoid search intensity and clutch size decisions were observed.
• 6 Parasitoids developing on second instar (low quality) hosts experienced high levels of mortality late during development and yielded very small adults.
• 7 The discord between these experimental results and predictions regarding the importance of egg load underscores the need for additional work on the proximate basis for host-feeding decisions and the nutritional ecology of insect parasitoids.

     

Influence of host density on the reproductive strategy of Cephalonomia stephanoderis, a parasitoid of the coffee berry borer

The effect of the density of the coffee berry borer, Hypothenemus hampei (Coleoptera: Scolytidae) on reproductive and host-feeding behaviours of the parasitoid Cephalonomia stephanoderis (Hymenoptera: Bethylidae) was evaluated under laboratory conditions. The number of hosts used for oviposition was density-dependent at low host density. Beyond a density of six hosts/day, the oviposition rate reached a maximum of 1.2 eggs/day due to egg limitation. Cephalonomia stephanoderis females responded to increasing host availability with a linear increase in host feeding. Overall, parasitoids killed more coffee berry borers by feeding and paralysis than by parasitism. At low host density, the pre-oviposition phase was extended, oogenesis was delayed, more males were produced, and host feeding occasionally occurred concurrently with oviposition. We suggest that the efficacy of C. stephanoderis as a biological control agent depends on seasonal variations in host density. Inoculative vs inundative releases in coffee plantations are discussed in relation to the abundance of the coffee berry borer during the fructification and interharvest periods.     

Effects of time limitation and egg limitation on lifetime reproductive success of a parasitoid in the field

We used field observations of freely foraging Aphytis aonidiae parasitoids in conjunction with results of laboratory studies of A. aonidiae and other Aphytis species to simulate lifetime patterns of behavior and reproduction. Field observations provided estimates of encounter rates with three classes of hosts, the mortality rate from predation on adult parasitoids, and host-handling times for oviposition and host feeding by adult wasps. A series of physiological parameters, including the egg maturation rate and the value of host-feeding meals, were estimated from previously published studies. Plasticity in parasitoid behavior was incorporated in two ways. For one set of simulations we used a behavioral rule derived empirically from observations of parasitoids made in the field, and for another we used a dynamic state-variable model to generate a set of behavioral rules that maximize lifetime reproductive success. As was expected, the empirically derived rule led to better matches with field observations than did simulations using the output of the dynamic model. Projections of lifetime reproductive success in the field ranged between three and 37 eggs within the 95% confidence intervals of the mortality rate and host encounter rate and depending on which behavioral rule was used. Lifetime reproductive success from the simulation with central estimates of the mortality and host encounter rates that incorporated the empirical rule was 6.25 eggs. Using the empirical versus the theoretical rule in the simulations led to a 10%-30% decline in projections of lifetime reproductive success, depending on mortality and host encounter rates. Regardless of the behavioral rule, the simulations underscored the observation that the host encounter rate was greater than the egg maturation rate. The overall oviposition rate was sufficiently high to lead to daily episodes of temporary egg limitation during which parasitoids must mature an egg before being able to oviposit.     

Asymmetric effects of adult nutrition on reproductive success of male and female Diaeretiella rapae (Hymenoptera: Aphidiidae)

The role of diet supplements (honey, water or no supplements) on egg maturation, oviposition strategy and longevity of the parasitic wasp Diaeretiella rapae McIntosh (Hymenoptera: Aphidiidae) is investigated. Parasitoids feed as larvae on hosts to acquire nutrition for growth and development, and further gain additional resources during their adult stage by feeding on either host or nonhost resources. The additional resources acquired by adults can help them to increase their reproductive activity or life expectancy, or both. Diaeretiella rapae females emerge with some developed eggs and no additional resources are required for egg maturation or successful oviposition. Females are able to oviposit and produce viable offspring immediately after emergence, and the number of eggs left in the ovaries of females decreases with subsequent oviposition, suggesting that ovigeny index of D. rapae is inclined towards pro‐ovigenic status. When unmated males and females are offered honey solution, females are attracted to it, whereas males display courtship and make mating attempts but then feed on honey after mating. The oviposition efficiency of female D. rapae increases by 30% when they feed on honey compared with when starved. Honey‐fed D. rapae adults live significantly longer (almost twice as long) than starved adults. Honey‐fed females deprived of hosts live longer than those offered hosts regularly. The positive effects of honey‐feeding on longevity are greater in females than in males. Taken together, the results of the present study suggest that the provision of additional resources to adult D. rapae parasitoids could enhance their life expectancy and parasitism efficiency in biological control programmes.