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.     

Effect of biotic and abiotic factors on reproductive parameters of the synovigenic endoparasitoid Venturia canescens

Abstract.  The main effects and interactions of adult age, access to food and host deprivation, on the egg load of Venturia canescens (Gravenhorst) (Hymenoptera: Ichneumonidae), a larval parasitoid of Ephestia kuehniella (Lepidoptera: Pyralidae) and other pyralids, were studied in the laboratory. Intraspecific variation in the number of ovarioles was also studied. There was a positive and significant correlation between wasp size and both egg load and ovariole number, with the reproductive system of large wasps containing significantly more ovarioles and mature eggs than small wasps. Newly emerged adult wasps contained 27 ± 2.4 ovulated (mature) eggs in their lateral oviducts. Access to food and host deprivation were the only conditions under which egg load increased with parasitoid age. Wasps that had access to hosts immediately after emergence showed a significant decline in their egg complement, irrespective of food presence. Under conditions of both host and food deprivation, there was practically no alteration of egg load with parasitoid age. A three-way analysis of variance revealed that egg load varies significantly with food or host access but not with parasitoid age. All interactions among the three factors were significant. It is confirmed that there is no egg resorption in V. canescens and that egg production stops in the absence of food.     

Superparasitism and host discrimination in the solitary ectoparasitoid Dinarmus basalis

In the solitary ectoparasitoid, Dinarmus basalis (Hymenoptera: Pteromalidae), the occurrence of superparasitism according to the unparasitised host density, and the nature of the host(s) provided was investigated in laboratory studies. In this species superparasitism was observed whatever the experimental conditions used, but the degree of superparasitism depended on the density of its host, Bruchidius atrolineatus (Coleoptera: Bruchidae). Superparasitism was due to successive egg-laying phases on the same host. However, females were able to discriminate between unparasitised hosts and hosts parasitised from 8 h to 72 h beforehand by themselves or by conspecifics. There was no conclusive evidence that superparasitism in the presence of a host parasitised 30 min before was linked to an absence of host discrimination. Host discrimination in this species is achieved by host-quality markers. These are individual-specific markers since conspecific superparasitism rates were often higher than self superparasitism rates. One deterrent substance is emitted by the females during oviposition onto the egg or released by the 16 to 24 h-old egg itself. Another host-quality marker is associated with the presence of a larva on its host. On the other hand, host discrimination ability did not always imply avoidance of superparasitism. In D. basalis there exists a positive relationship between the survival probability of the second egg and the tendency to superparasitise, and superparasitism could therefore result in a significant fitness gain. Under our experimental conditions, D. basalis females exhibited a wide range of oviposition behavioural plasticity in relation to the parasitoid developmental stage, the type of superparasitism, and the encounter rate with unparasitised hosts.     

Costs of reproduction and geographic variation in the reproductive tactics of the mosquito Aedes triseriatus

Intraspecific host discrimination is widespread in solitary parasitoids whose adult females forage for and evaluate host suitability, whereas interspecific discrimination is less common. In some parasitoid species, mostly Diptera and Coleoptera, the larva performs the last step of host searching. It has been suggested that host discrimination will rarely occur in such host-seeking larvae because their low mobility results in a low host encounter rate. We determined the extent to which the larvae of Aleochara bilineata Gyllenhal (Coleoptera: Staphylinidae), a solitary parasitoid of aggregated Diptera pupae: (1) discriminated between unparasitized hosts and hosts parasitized by conspecifics; (2) used semiochemical cues to discriminate; (3) were influenced by life expectancy, presence of conspecifics and host availability in their host acceptance decision; and the extent to which (4) A. bilineata and A. bipustulata L., a species exploiting the same hosts and occurring sympatrically, showed interspecific host discrimination. A. bilineata larvae were able to discriminate between unparasitized hosts and hosts parasitized by conspecifics in a choice experiment. Such behavior has never previously been described for a coleopteran parasitoid or for a parasitoid species whose larvae perform host searching. Host discrimination in this species was not based on the presence of visual or tactile cues (e.g., entrance holes) but rather on chemical cues. The life expectancy of A. bilineata larvae was significantly shorter in the presence than in absence of hosts, and older larvae had lower parasitism success than young larvae in a 24-h experiment. However, the host acceptance decision of A. bilineata larvae was not influenced by larval age or the presence of conspecifics when the ratio of hosts per larva was greater than or equal to 1. When hosts were scarce, the degree of superparasitism increased significantly with the number of foraging conspecifics and the age of the larvae. Both species of Aleochara showed intra- and interspecific host discrimination in a choice experiment. In contrast to A. bipustulata, A. bilineata larvae more frequently parasitized hosts parasitized by A. bipustulata than those parasitized by conspecifics. We suggest that host discrimination will be frequent in solitary parasitoids with host-seeking larvae when hosts are aggregated. Received: 4 June 1998 / Accepted: 1 September 1998     

Host discrimination modulates brood guarding behaviour and the adaptive superparasitism in the parasitoid wasp Trissolcus semistriatus (Hymenoptera: Scelionidae)

Because hosts utilized by parasitoids are vulnerable to further oviposition by conspecifics, host guarding benefits female wasps. The present study aims to test whether female adults regulate brood guarding behaviour by host discrimination in a solitary parasitoid Trissolcus semistriatus by presenting an intact or parasitized host egg mass to a female adult. Virgin females without oviposition experience have host discrimination ability, which enables them to adjust the number of eggs laid in the hosts. Mating experience increases superparasitism by female adults, whereas mated females achieve a higher discrimination ability as a result of oviposition experience and show a lower superparasitism rate. As expected, females exhibit brood guard after parasitizing an intact host egg mass, whereas those females visiting a previously parasitized host egg mass, do not. Because the survival of eggs in superparasitized hosts is relatively low, regulating brood guarding behaviour by host discrimination is adaptive for female wasps.     

Occurrence of Cephalonomia stephanoderis Betrem (Hymenoptera: Bethylidae) in coffee plantations of the Brazilian Amazonia

Adults of Cephalonomia stephanoderis Betrem were detected (in November 2003) during the sampling of Coffea canephora Pierre ex A. Froehner berries damaged by Hypothenemus hampei Ferrari (Coleoptera: Scolytidae) in Ouro Preto D'Oeste - Rond?nia, Brazil (10 degrees 45'S and 62 degrees 15'W). From January to July 2004, the parasitoid was monthly sampled in 200 berries damaged by H. hampei. Probably, C. stephanoderis can already exert some parasitism pressure at the coffee berry borer population. The occurrence of this parasitoid in natural conditions points out to another alternative for the biological control of the H. hampei in Rond?nia. This is the first record of C. stephanoderis in coffee plantations of the Brazilian Amazonia.     

Herbivore egg deposition induces tea leaves to arrest the egg‐larval parasitoid Ascogaster reticulata

Plants are able to activate direct and indirect defences against egg deposition by herbivorous insects. A known indirect defence is the production of synomones to help egg‐ and egg‐larval parasitoids to locate their hosts. The wasp Ascogaster reticulata Watanabe (Hymenoptera: Braconidae) is a solitary egg‐larval parasitoid of the moth Adoxophyes honmai Yasuda (Lepidoptera: Tortricidae), which lays eggs and feeds as caterpillars on the leaves of the tea plant Camellia sinensis (L.) Kuntze (Theaceae). Here, we studied whether or not oviposition by A. honmai induces tea plants to produce synomones that help the parasitoid to locate its host. An olfactometer bioassay suggested that synomones produced by the infested plants did not attract the parasitoid over a short range. However, a contact bioassay showed that tea leaves were induced to arrest the parasitoid 24 h after egg deposition and remained induced until the host‐egg masses were no more attractive to the parasitoids. Wing scales and deposits of adult moths and the contents of the egg masses did not induce the tea leaves to arrest the parasitoid, but the contents of the female moth's reproductive system did. Synomone induction was systemic: uninfested leaves in the vicinity of egg‐laden leaves also arrested the parasitoid.     

Catching Ariadne by her thread: how a parasitoid exploits the herbivore's marking trails to locate its host

Chemical signals that can be associated with the presence of a host insect often work as arrestants in close range host location by parasitoids, leading to longer searching times on patches where such signals are present. Our current view of parasitoid host location is that by prolonging the search times in patches, randomly searching parasitoids enhance their chance of detecting host insects. However, prolonged search times are not necessarily the only modification in parasitoid behaviour. In this study, we examine the exploitation of host-fruit marking pheromone of rose-hip flies, Rhagoletis basiolaOsten-Sacken (Diptera: Tephritidae) by the specialized egg-larval parasitoid Halticoptera rosae Burks (Hymenoptera: Pteromalidae). We provide evidence that the instantaneous probability that a host egg will be located by a searching parasitoid wasp differs markedly between pheromone-marked and unmarked fruits. The arresting response to the marking pheromone, i.e., the prolonged time a wasp is willing to search on marked fruits, can only account for a small fraction of the difference in successful host location on marked and unmarked fruits. We further demonstrate that the time wasps require to locate the host egg is independent of the size of the rose-hip harbouring the fly egg, and thus is independent of the area the wasp potentially has to search. A comparison of our findings with results of different search algorithms for parasitoid wasps suggests that wasps use the fly's pheromone marking trail as a guide way to the fly's oviposition site and thus the host egg.     

Discrimination of the age of conspecific eggs by an ovipositing ectoparasitic wasp

The recognition and avoidance of already parasitized hosts is a major issue in parasitoid behavioural ecology. A key factor affecting the fitness reward expected from superparasitism is the probability that the second or subsequent egg laid on a host will win the contest with the first-laid egg. The present study investigated the ability of females of the solitary ecto parasitoid Anisopteromalus calandrae Howard (Hymenoptera: Pteromalidae) to (i) discriminate between unparasitized Callosobruchus maculatus (Fabricius) (Coleoptera: Bruchidae) hosts and those parasitized by a conspecific, and (ii) discriminate between a host parasitized by an egg just laid (2 h) and one parasitized by an egg about to hatch (28 h). However, they did not adjust their offspring sex ratio on already parasitized hosts compared to unparasitized ones. Our results show that A. calandrae females can discriminate between parasitized and unparasitized hosts, as they lay more eggs on the latter. The probability of the second or subsequent egg laid on a host (superparasitism) winning the contest with a conspecific increases as the time between the two ovipositions decreases. Consequently, parasitoid females should lay more eggs on recently parasitized hosts than on those that have been parasitized for a long time (i.e., when the first eggs are about to hatch), and that is indeed what they were found to do. To increase their fitness in spite of the presence of already parasitized hosts, A. calandrae females have developed highly discriminative capacities regarding the parasitism status of hosts.     

Reciprocal influences and costs of parasitism on the development of Corcyra cephalonica and its endoparasitoid Venturia canescens

Many endoparasitoids develop successfully within a range of host instars. Parasitoid survival is highest when parasitism is initiated in earlier host instars, due to age-related changes in internal (physiological) host defences. Most studies examining fitness-related costs associated with differences in host instar have concentrated on the parasitoid, ignoring the effects of parasitism on the development of surviving hosts that have encapsulated parasitoid eggs. A laboratory experiment was undertaken examining fitness-related costs associated with encapsulation of Venturia canescens (Hymenoptera: Ichneumonidae) eggs by fifth (L5) instar larvae of Corcyra cephalonica (Lepidoptera: Pyralidae). Growth and development of both host and parasitoid were monitored in C. cephalonica larvae containing 0, 1, 2, or 4 parasitoid eggs. Adult size and fecundity of C. cephalonica did not vary with the number of eggs per host. However, there was a distinct increase in host mortality with egg number, although most parasitoids emerged from hosts containing a single egg. The most dramatic effect on the host was a highly significant increase in development time from parasitism to adult eclosion, with hosts containing 4 parasitoid eggs taking over 2.5 days longer to complete development than unparasitized larvae. The egg-to-adult development time and size of adult V. canescens did not vary with egg number per host, as demonstrated in a previous experiment using a different host (Plodia interpunctella). The results described here show that there are fitness-related costs to the host associated with resistance to parasitism.     

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     

Role of volatile semiochemicals in host location by the egg parasitoid Anagrus breviphragma

Recent investigations conducted on several tritrophic systems have demonstrated that egg parasitoids, when searching for host eggs, may exploit plant synomones that have been induced as a consequence of host oviposition. In this article we show that, in a system characterized by host eggs embedded in the plant tissue, naïve females of the egg parasitoid Anagrus breviphragma Soyka (Hymenoptera: Mymaridae) responded in a Y‐tube olfactometer to volatiles from leaves of Carex riparia Curtis (Cyperaceae) containing eggs of one of its hosts, Cicadella viridis (L.) (Hemiptera: Cicadellidae). The wasp did not respond to host eggs or to clean leaves from non‐infested plants compared with clean air, whereas it showed a strong preference for the olfactometer arm containing volatiles of leaves with embedded host eggs, compared with the arm containing volatiles of leaves from a non‐infested plant or host eggs extracted from the plant. When the eggs were removed from an infested leaf, the parasitoid preference was observed only if eggs were added aside, suggesting a synergistic effect of a local plant synomone and an egg kairomone. The parasitoid also responded to clean leaves from an egg‐infested plant when compared with leaves from a non‐infested plant, indicating a systemic effect of volatile induction.     

Influence of host diet on parasitoid fitness: unravelling the complexity of a temperate pastoral agroecosystem

Parasitoid fitness is closely associated with the condition of the host insect, and the condition of the host is partly dependent on the quality and quantity of plant food available. The relationship between host diet and parasitoid fitness therefore has the potential to indirectly mediate complex multitrophic interactions. This relationship may be influenced both by the presence of mycotoxins from endophytic fungi, which share symbiotic relationships with plants and cause reductions in host-plant quality for herbivores, and by the availability of beneficial nutrient-rich plant foods such as pollen. This study used a multitrophic system involving ryegrass, a fungal endophyte, pollen, and an insect herbivore and its parasitoid to study the effect of host diet on parasitoid fitness. Previous studies showed that the larval stage of the parasitoid was negatively influenced by the presence of fungal-derived alkaloids in the diet of its host, but no assessment of effects on the adult stage of the parasitoid had been made. Similarly, the effect of pollen in the diet of the host on the fitness of the parasitoid had not previously been examined. In this study, the fitness of parasitoids reared from hosts fed endophyte-free ryegrass, endophyte-free ryegrass plus pollen, or endophyte-infected ryegrass was assessed in two laboratory experiments. Host insects exhibited significant responses to treatment, but remarkably, there were no significant treatment effects on parasitoid development times, the number of successful parasitoid emergences, tibia length, or preoviposition egg complement. The absence of a strong relationship between host diet and parasitoid fitness in this study differs markedly from studies of other parasitoid–host systems in that the adult stage of this parasitoid appears remarkably unresponsive to variation in host condition. This work contributes to a better understanding of multitrophic interactions and to the refinement of integrated pest management tactics in a temperate pastoral agroecosystem.     

Host-feeding and oviposition by parasitoids in relation to host stage: Consequences for parasitoid-host population dynamics

Among parasitoids which host-feed destructively, there is a tendency for females to partition their feeding and oviposition behaviour in relation to different host stages, feeding preferentially or exclusively on earlier host stages and ovipositing preferentially or exclusively in (or on) later ones. We explored the dynamic implications of this behaviour for parasitoid-host population dynamics, using modifications of the age-structured simulation models of Kidd and Jervis (1989, 1991). Using the new versions of the models, we compared the situation where parasitoids practice host stage discrimination with respect to feeding and oviposition, with the situation where they do not. Additionally, we examined the effects of host stage discrimination on populations by (a) having generations either discrete or overlapping, (b) varying initial age structure, (c) having varying degrees of density dependence acting on host adult mortality, and (d) varying parasitoid develoment times in relation to the length of host development. With either discrete or overlapping generations of the host population, a reduction in the parasitoid development time had a destabilizing influence on the parasitoid-host population interaction. With discrete generations stage discrimination had no effect on the risk of extinction, irrespective of either the degree of density dependence acting on the host population, or the initial age structure of the host population. When parasitoid search was uncoupled from the insect's adult energy requirements, the interaction was always unstable. With continuous generations, stage discrimination affected stability at certain parasitoid development times, but not at others. The relative lengths of parasitoid and host development times also influenced the tendency of the host population to show discrete or overlapping generations.     

Interactions between the egg and larval parasitoids of a gall-forming midge and their impact on the host

1. The gall‐forming midge Rhopalomyia californica was exposed experimentally to parasitism and predation during only the egg stage, during only the larval stage, during neither stage, or during both stages. 2. The combined action of natural enemies that attack during both the egg stage and the larval stage led to the lowest number of midges and total insects (midges + parasitoids) in the next generation, and the highest percentage parasitism. 3. The larval parasitoid killed a large fraction of hosts without producing new parasitoid offspring, while there is some indication that the egg parasitoid on its own tended to produce the most parasitoid offspring. The contrasting implications of host mortality versus parasitoid production for biological control are discussed. 4. Exposure to larval parasitoids resulted in a reduction in the number of egg parasitoid offspring produced, but exposure to the egg parasitoid did not affect the number of larval parasitoid offspring produced significantly.     

Maternally induced host regulation by the egg parasitoid Telenomus heliothidis

ABSTRACT. The egg parasitoid Telenomus heliothidis Ashmead (Hymenoptera: Scelionidae) arrested development and prevented emergence of its host, the egg of Heliothis virescens F. (Lepidoptera: Noctuidae). Arrestment was due to a factor injected by the ovipositing parasitoid just prior to egg release. T. heliothidis prevented hatching of H. virescens eggs up to 62 h old. Implantation of the distal region of the parasitoid common oviduct also prevented host emergence. Examination of the distal common oviduct revealed large numbers of protein-containing vesicles in the cytoplasm of the oviduct epithelial cells. These vesicles may be the source of the arrestment factor. The arrestment factor did not prevent emergence of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae), an interspecific competitor of T. heliothidis.     

拟寄生蜂搜索产卵过程中对寄主的竞争

综述拟寄生蜂搜索产卵过程中对寄主竞争的最新研究进展.这类竞争具有四种方式,即标记寄主、杀卵和杀幼、守护寄主和捕食寄主.（1）标记寄主常涉及寄主标记信息素,这是由雌蜂在产卵前、产卵时或产卵后分泌的化学物质.寄主标记信息素常介导拟寄生蜂对已寄生和健康寄主的辨别、减少过寄生和多寄生、减轻种内和种间竞争压力.（2）雌蜂遇到已寄生寄主时,很多种类杀死前一雌蜂遗留的卵和幼虫,再产下自己的卵.雌蜂使用三种方法杀卵和杀幼,即产卵器穿刺、取食和使用有毒物质.通过杀卵和杀幼,产卵雌蜂清除了前一雌蜂遗留的后代,主动改善了寄主品质,从而有利于自身后代的生存.（3）守护寄主在肿腿蜂科、缘腹细蜂科、金小蜂科、缨小蜂科和茧蜂科中均有报道,守护者驱逐入侵者以保护后代及健康寄主.（4）捕食寄主不仅减少了健康寄主数量,且直接导致已寄生寄主中拟寄生蜂卵和幼虫的死亡.雌蜂一般在体内成熟卵量较少时捕食寄主.讨论了研究拟寄生蜂搜索产卵过程中竞争寄主的理论意义和实际应用价值.     

Reproduction now or later: optimal host-handling strategies in the whitefly parasitoid Encarsia formosa

We developed a dynamic state variable model for studying optimal host‐handling strategies in the whitefly parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae). We assumed that (a) the function of host feeding is to gain nutrients that can be matured into eggs, (b) oögenesis is continuous and egg load dependent, (c) parasitoid survival is exponentially distributed and (d) parasitoids encounter hosts randomly, are autogenous and have unlimited access to non‐host food sources to obtain energy for maintenance and activity. The most important prediction of the model is that host feeding is maladaptive under field conditions of low host density (0.015 cm^?2) and short parasitoid life expectancy (maximum reproductive period of 7 d). Nutrients from the immature stage that can be matured into eggs are sufficient to prevent egg limitation. Both host density and parasitoid life expectancy have a positive effect on the optimal host‐feeding ratio. Parasitoids that make random decisions gain on average only 35% (0.015 hosts cm^?2) to 60% (1.5 hosts cm^?2) of the lifetime reproductive success of parasitoids that make optimal decisions, independent of their life expectancy. Parameters that have a large impact on lifetime reproductive success and therefore drive natural selection are parasitoid life expectancy and the survival probability of deposited eggs (independent of host density), the number of host encounters per day (when host density is low) and the egg maturation rate and number of host types (when host density is high). Explaining the evolution of host‐feeding behaviour under field conditions requires field data showing that life expectancy in the field is not as short as we assumed, or may require incorporation of variation in host density. Incorporating variation in walking speed, parasitised host types or egg resorption is not expected to provide an explanation for the evolution of host‐feeding behaviour under field conditions.     

Costs and benefits of host feeding in the parasitoid wasp Trichogramma turkestanica

Females of the parasitoid wasp Trichogramma turkestanica Meyer (Hymenoptera: Trichogrammatidae) generally host feed after ovipositing on the first egg of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) they encounter. We measured the impact of host feeding on the fecundity and longevity of females, in absence of host or food, and on the fitness of their progeny. We also determined if the frequency of host feeding is influenced by the humidity level at which T. turkestanica females developed. Host feeding increased egg production by 70% but decreased female longevity. This impact of host feeding on the longevity of females is probably due to the allocation of carbohydrates to egg production at the expense of somatic maintenance. Humidity did not influence the occurrence or duration of host feeding. The size of individuals developing in eggs on which females host fed was smaller, indicating that their fitness was affected.     

Effect of adult feeding and timing of host exposure on the fertility and longevity of the parasitoid Anaphes flavipes

The parasitoid Anaphes flavipes (Foerster) (Hymenoptera: Mymaridae) is a gregarious egg parasitoid which is widely used in biological control against important crop pest beetles of the genus Oulema (Coleoptera: Chrysomelidae). Here, we present the first experimental examination of the influence of adult feeding and timing of host exposure on the longevity and fertility of this parasitoid. We confirmed a positive effect of adult feeding on longevity of both sexes. Fed parasitoids lived 3× longer than unfed ones. On the other hand, adult feeding and feeding time had no effect on female fertility. The number of hatched offspring was not increased by adult feeding, which suggests that the parasitoid emerges with already mature ovaries (proovigenic type). However, the fertility of fed females was strongly influenced by the timing of host egg exposure. By providing distinct groups of parasitoids with host eggs at different times, we were able to show lower fertility of fed females that had been offered host eggs more than 24 h after hatching. Our results thus show that the parasitoid's fertility is determined by her age at the time of parasitization rather than by feeding.