Time limitation, egg limitation, the cost of oviposition, and lifetime reproduction by an insect in nature

For more than 80 years, ecologists have debated whether reproduction by female insect herbivores and parasitoids is constrained by the time needed to find hosts (time limitation) or by the finite supply of mature eggs (egg limitation). Here we present the first direct measures of permanent time limitation and egg limitation and their influences on the cost of oviposition and lifetime reproduction for an insect in nature. We studied the gall midge Rhopalomyia californica, which neither matures nor resorbs eggs during the adult stage. By sampling females soon after their death and correcting for predation effects, we demonstrate that females lay a large proportion of their total complement of eggs (multiyear mean: 82.9%). The egg supplies of 17.1% of females were completely exhausted, with the remaining 82.9% of females being time limited. As predicted by theory, we estimate that even though egg limitation is a minority condition within the population, egg costs make a substantial contribution (57% of the total) to the cost of oviposition. We conclude that insect life histories evolve to produce a balanced risk of time and egg limitation and, therefore, that both of these constraining factors have important influences on insect oviposition behavior and population dynamics.     

Rate of nutrient allocation to egg production in a parasitic wasp

Recent years have seen a marked increase in our awareness of the need to incorporate greater physiological realism into studies of parasitoid behaviour and population dynamics. Quantification of the number of eggs produced as a result of a host-feeding event, the host-feeding gain, is essential for predicting when a parasitoid should bypass an opportunity for current reproduction (i.e. laying eggs) in order to feed from the host and, thus, increase its chances for future reproduction (i.e. producing further eggs). Using radioactively labelled amino acids, one of the main constituents of insect haemolymph, we followed the incorporation of a known quantity of nutrients into each individual egg laid over a long period of time relative to the average life span of the parasitoid. Although the maximum incorporation of nutrients obtained by the female from a discrete feeding event occurs within a short period of time, a large proportion of nutrients are stored and used gradually for egg production throughout the life of the parasitoid. We therefore provide novel experimental evidence showing that feeding gain is not a discrete event in time occurring shortly after feeding, as has so far been assumed, but is instead spread throughout the parasitoid''s lifetime. This has important consequences for calculating the increase in lifetime fitness as a result of a feeding event, a common currency of models that aim to predict feeding and oviposition behaviour in parasitoids.     

Age-dependent clutch size in a koinobiont parasitoid

Abstract.  1. The Lack clutch size theory predicts how many eggs a female should lay to maximise her fitness gain per clutch. However, for parasitoids that lay multiple clutches it can overestimate optimal clutch size because it does not take into account the future reproductive success of the parasitoid.
2. From egg-limitation and time-limitation models, it is theoretically expected that (i) clutch size decreases with age if host encounter rate is constant, and (ii) clutch size should increase with host deprivation and hence with age in host-deprived individuals.
3. Clutch sizes produced by ageing females of the koinobiont gregarious parasitoid Microplitis tristis Nees (Hymenoptera: Braconidae) that were provided daily with hosts, and of females ageing with different periods of host deprivation were measured.
4. Contrary to expectations, during the first 2 weeks, clutch size did not change with the age of the female parasitoid, neither with nor without increasing host-deprivation time.
5. After the age of 2 weeks, clutch size decreased for parasitoids that parasitised hosts daily. The decrease was accompanied by a strong decrease in available eggs. However, a similar decrease occurred in host-deprived parasitoids that did not experience egg depletion, suggesting that egg limitation was not the only factor causing the decrease in clutch size.
6. For koinobiont parasitoids like M. tristis that have low natural host encounter rates and short oviposition times, the costs of reproduction due to egg limitation, time limitation, or other factors are relatively small, if the natural lifespan is relatively short.
7. Koinobiont parasitoid species that in natural situations experience little variation in host density and host quality might not have strongly evolved the ability to adjust clutch size.     

Theory of oviposition strategy of parasitoids. I. Effect of mortality and limited egg number

The optimal oviposition strategies of parasitoids, the host range, and the number of eggs laid per host which result in the maximum lifetime performance of reproduction, are investigated. To study the effects of parasitoid mortality and of limiting total number of eggs laid by a parasitoid, a standard criterion used in previous theories of optimal diet and optimal patch use, the maximization of the foraging rate, is no longer suitable. The model is solved analytically by using dynamic programming. The results are as follows: The host preference of solitary parasitoids depends on the mortality during handling times; i.e., the forager tends to avoid hosts with high risk of foraging mortality. If the total number of eggs produced by a parasitoid is limited, and if the mortality during handling is negligible, the host range is wider when a larger number of eggs remains in the parasitoid's body. In general, however, the mortality-cost of forager and the egg-cost interplay, because the loss of future reproduction by mortality increases with the number of available eggs. In an example with two host types, host range is widest with an intermediate number of eggs available in the body. The optimal number of eggs per host laid by a gregarious parasitoid is also affected by the differential mortality of the forager, and by the number of available eggs.     

THE RESISTANCE OF INSECT PARASITOIDS TO THE DEFENCE REACTIONS OF THEIR HOSTS

Some of the following propositions are to be read as suggestions or hypotheses, supported by circumstantial or direct evidence, but not yet rigorously demonstrated. An estimate of the significance to be attached to each should be gathered from the body of the paper rather than from the following brief statements. 1.The problem is posed: how do endophagous parasitoids counteract the haemocytic defence reactions of their usual hosts? 2.It has been demonstrated that the egg and young first-instar larva of Nemeritis canescens have a coating on their surface which enables them to escape the attention of the haemocytes of their usual host, and to develop without exciting a defence reaction. The coating is applied to the egg before it is laid, and to the cuticle of the larva before it hatches. A little evidence suggests that some other ichneumon wasps of the subfamily Ophioninae may use this mechanism of resistance. 3.Older first-instar larvae, and the second and later instars, of many parasitoids, both hymenopterous and dipterous, probably overcome the haemocytic reaction of their host by rapid feeding, which depletes its blood both of cells and of nutrients, and so drains its resources that haematopoiesis is prevented and encapsulation becomes impossible. 4.The common habit of parasitoids of lingering in the first instar, before ingesting much food, while the host goes on developing to another stage or undergoes diapause, may enable the larva to retain a protective coating that would have become ineffective if it had grown. When at length the larva does feed and grow, the preceding mechanism (3) comes into play. 5.The teratocytes and pseudogerms formed by many species in several families of Hymenoptera absorb nutrients on a large scale from the blood of the host. They act quickly, as soon as the larva hatches. I suggest that by their attrition of the host's reserves of food, and its consequent debility, they prevent an effective haemocytic reaction to the young parasitoid. 6.Some dipterous and hymenopterous parasitoids first inhabit the intestine of their host, and do not penetrate the body cavity until they are ready to overwhelm the defence reactions by rapid and gross feeding. 7.Parasitoids that live temporarily inside an organ of the host may there acquire a coating which protects them from reaction by the blood cells. 8.Species of parasitoids that occupy an organ of the host for a long period, and develop inside it, escape a defence reaction because they live within the connective tissue covering the organ, to which the blood cells do not react. 9.Eggs of hymenopterous parasitoids laid within the embryos of their hosts may be treated by the embryonic blood cells as a developing organ, and become covered with connective tissue as those organs are. Thereafter they would not be recognized as foreign bodies. 10.Parasitoid eggs laid in the eggs or the young larvae of their host may be coated with host substances, or covered by connective tissue (9), before the blood of the host be comes capable of vigorousdefence reactions. They would there after escape recognition as foreign bodies. This may be the advantage of the habit of the so-called egg-larval parasitoids. 11.Reasons have been given by Schneider (1950) for his belief that the serosa of the ichneumon wasp Diplazon fissorius secretes something that locally inhibits the defence reactions of its hosts. The trophamnion and pseudoserosa of some parasitoid eggs may have this function. 12. Some parasitoids, especially second- and third-instar larvae of Tachinidae, physically repulse the haemocytes of their host, moulding them into a capsule that serves the maggot as a respiratory sheath.     

SEVERE COSTS OF REPRODUCTION PERSIST IN ANOLIS LIZARDS DESPITE THE EVOLUTION OF A SINGLE‐EGG CLUTCH

A central tenet of life‐history theory is that investment in reproduction compromises survival. We tested for costs of reproduction in wild brown anoles (Anolis sagrei) by eliminating reproductive investment via surgical ovariectomy and/or removal of oviductal eggs. Anoles are unusual among lizards in that females lay single‐egg clutches at frequent intervals throughout a lengthy reproductive season. This evolutionary reduction in clutch size is thought to decrease the physical burden of reproduction, but our results show that even a single egg significantly impairs stamina and sprint speed. Reproductive females also suffered a reduction in growth, suggesting that the cumulative energetic cost of successive clutches constrains the allocation of energy to other important functions. Finally, in each of two separate years, elimination of reproductive investment increased breeding‐season survival by 56%, overwinter survival by 96%, and interannual survival by 200% relative to reproductive controls. This extreme fitness cost of reproduction may reflect a combination of intrinsic (i.e., reduced allocation of energy to maintenance) and extrinsic (i.e., increased susceptibility to predators) sources of mortality. Our results provide clear experimental support for a central tenet of life‐history theory and show that costs of reproduction persist in anoles despite the evolution of a single‐egg clutch.     

ON THE EVOLUTION OF PARTHENOGENESIS. II. INBREEDING AND THE COST OF MEIOSIS

Quantitative models of genetic change were analyzed to study the effect of inbreeding on the conditions for the evolution of parthenogenesis. Although inbreeding has been proposed as a key factor that may resolve the apparent paradox between the success of biparental reproduction and the genetic advantages of uniparental reproduction, the results indicate that inbreeding does not greatly change the cost of meiosis in diploids and actually increases it in haplodiploids. Inbreeding increases parent-offspring relatedness and the reproductive value of females. These direct effects act antagonistically on the cost of meiosis: higher relatedness between parents and biparentally-derived offspring promotes biparental reproduction, and high reproductive value of females promotes thelytoky. In diploids the two effects cancel one another, while in haplodiploids the latter predominates. A survey by Hamilton (1967) showed that a high proportion of haplodiploid species that undergo close inbreeding have thelytokous relatives, an association that is consistent with the result obtained here that, apart from its effect on the sex ratio, inbreeding directly promotes parthenogenesis in haplodiploids.     

Cost of reproduction in a long-lived bird: incubation effort reduces immune function and future reproduction

Life-history theory predicts that increased current reproductive effort should lead to a fitness cost. This cost of reproduction may be observed as reduced survival or future reproduction, and may be caused by temporal suppression of immune function in stressed or hard-working individuals. In birds, consideration of the costs of incubating eggs has largely been neglected in favour of the costs of brood rearing. We manipulated incubation demand in two breeding seasons (2000 and 2001) in female common eiders (Somateria mollissima) by creating clutches of three and six eggs (natural range 3-6 eggs). The common eider is a long-lived sea-duck where females do not eat during the incubation period. Mass loss increased and immune function (lymphocyte levels and specific antibody response to the non-pathogenic antigens diphtheria and tetanus toxoid) was reduced in females incubating large clutches. The increased incubation effort among females assigned to large incubation demand did not lead to adverse effects on current reproduction or return rate in the next breeding season. However, large incubation demand resulted in long-term fitness costs through reduced fecundity the year after manipulation. Our data show that in eiders, a long-lived species, the cost of high incubation demand is paid in the currency of reduced future fecundity, possibly mediated by reduced immune function.     

Fitness conflicts and the costs of sociality in communal egg layers: a theoretical model and empirical tests

Individuals within complex social groups often experience reduced reproduction owing to coercive or suppressive actions of other group members. However, the nature of social and ecological environments that favour individual acceptance of such costs of sociality is not well understood. Taxa with short periods of direct social interaction, such as some communal egg layers, are interesting models for study of the cost of social interaction because opportunities to control reproduction of others are limited to brief periods of reproduction. To understand the conditions under which communal egg layers are in fitness conflict and thus likely to influence each other's reproduction, we develop an optimality model involving a brood guarding 'host' and a nonguarding disperser, or 'egg dumper'. The model shows that when, where intermediate-sized broods have highest survival, lifetime inclusive fitnesses of hosts and dumpers are often optimized with different numbers of dumped eggs. We hypothesize that resolution of this conflict may involve attempts by one party to manipulate the other's reproduction. To test model predictions we used a lace bug (Heteroptera: Tingidae) that shows both hosts and egg dumpers as well as increased offspring survival in response to communal egg laying. We found that egg-dumping lace bugs oviposit a number of eggs that very closely matches predicted fitness optimum for hosts rather than predicted optimum of dumpers. This result suggests that dumpers pay a social cost for communal egg laying, a cost that may occur through host suppression of dumper reproduction. Although dumper allocation of eggs is thus sub-optimal for dumpers, previous models show that the decision to egg dump is nevertheless evolutionarily stable, possibly because hosts permit just enough dumper oviposition to encourage commitment to the behaviour.     

Ant queens adjust egg fertilization to benefit from both sexual and asexual reproduction

An enduring problem in evolutionary biology is the near ubiquity of sexual reproduction despite the inherent cost of transmitting only half the parent's genes to progeny. Queens of some ant species circumvent this cost by using selectively both sexual reproduction and parthenogenesis: workers arise from fertilized eggs, while new queens are produced by parthenogenesis. We show that queens of the ant Cataglyphis cursor maximize the transmission rate of their genes by regulating the proportion of fertilized and parthenogenetic eggs laid over time. Parthenogenetic offspring are produced in early spring, when workers raise the brood into sexuals. After the mating period, queens lay mostly fertilized eggs that will be reared as the non-reproductive caste.     

Egg distribution of insect parasitoids: a survey of models

A number of (insect) parasitoids have been found to avoid superparasitism, i.e., these parasitoids distribute their eggs more evenly over the available hosts than might be expected from chance only. By doing so each parasitoid individual ensures a greater probability of survival for its offspring as a result of a reduced within-host-competition.Recently a number of mathematical models have been developed, describing the distribution of the parasitoid eggs in the hosts. This paper gives a survey of these models, placing them within one and the same mathematical framework. An essential conceptual distinction, neglected up to now, emerges: parasitoids can either react to the number of previous visits to a particular host, or they can react to the number of eggs already present in that host.For each model the probability-generating function, the mean, the variance, and the probability distribution of the number of eggs are given, as well as a discussion of estimating and testing procedures. A few possibilities for generalizations of these models are discussed too.     

THE NATURAL CONTROL EFFECT OF EGG PARA-SITOIDS ON LITCHI STINK BUG TESSARATOMA PAPILLOSA (HETEROPTERA: PENTATOMIDAE) IN LITCHI ORCHARD

Abstract  The distribution of eggs of the litchi stink bug Tessaratoma papillosa Drury was observed. By marking the eggs of T. papillosa in an integrated pest managed litchi orchard and in an orchard with chemical control, respectively, the control effect of the egg parasitoids on T. papillosa in the two kinds of licthi orchards was investigated in Guangzhou in 1996. The female T. papillosa began to oviposit in mid-March and laid eggs vigorously from early April to early June, and then successively entered the declining stage of oviposition in 1996 in Guangzhou. 86% of the litchi stink bug eggs were laid in the peak period of oviposion. Two egg parasitoids, Anastatus japonicus and Ooencyrtus phongi , were obtained in the integrated managed litchi orchard. The rate of eggs parasitized by A. japonicus and O. phongi attained to 3.2% -18.4% and 3.2%-30.4%, respectively. The united attack of the two parasitoid wasps destroyed 30.6% - 47% host eggs in the middle and late stages of T. papillosa oviposition. Only A. japonicus was collected in the chemical controlled litchi orchard and the percentage of eggs parasitized by this wasp was only 0.2% -2.8%.     

Modifications of Trichogramma Behaviors During the Exploitation of Host Patches Induced by the Insecticide Chlorpyrifos

Parasitoid species are key species because they regulate numerous insect species, including pests. An efficient infestation of hosts is critical to the development of parasitoid populations. In this article, we investigate the effects of the widely used insecticide chlorpyrifos on the exploitation of a patch of host by a parasitoid, Trichogramma brassicae. We show that chlorpyrifos increased the efficiency of parasitoid females in the infestation of the first host egg by decreasing its super-parasitization. Except for the first egg, all infested eggs were infested only once by both control and treated females; therefore, the insecticide did not impede the detection of a host that had already been infested. We did find that the insecticide affected the mode of rejection of infested eggs. At the beginning of the exploitation of the patch, females exposed to the insecticide made more antennal rejections than controls but eventually made more ovipositor rejections. These results suggest that the insecticide initially stimulated the antennal perception of the infested host but finally led to the saturation of this perception. Parasitoids compensated for this loss of antennal perception via ovipositor perception of infested eggs. This switch of behavior corresponds to a decrease in efficiency, as it is much more time consuming; therefore, females exposed to the insecticide had to stay longer on the patch for an equal rate of exploitation relative to controls. The infestation of host eggs is a crucial behavior for parasitoids, enabling their reproduction and the development of their species. By decreasing the antennal recognition of infested eggs, chlorpyrifos continues to be detrimental even when parasitoids survive exposure.     

Reproduction and the energy cost of defense in a Batesian mimicry complex

Summary The amount of energy invested in reproduction and in defense was examined in a Batesian mimicry complex consisting of the modelEleodes obscura and the mimicStenomorpha marginata (both Coleoptera: Tenebrionidae). Models live up to 4 y as adults while mimic adults live only 3 mo. The energy content of the eggs of the model and mimic was determined by microbomb calorimetry. The energy content of the defensive secretions produced by the model was determined by computational chemistry and MNDO computer programming. Contrary to the predictions of some life-history theory, the long-lived model annually produces many small eggs each of low energetic content, while the short-lived mimic annually produces fewer, larger eggs each of high energetic content. However, in terms of total energy, the long-lived model has an annual investment in reproduction equal to that of the short-lived mimic. During the 3 mo of co-ocurrence of models and mimics within a year, an average individual model's cost in using defensive secretions against potential predators is 12% of the amount of energy tied up in the eggs that it produces within the year. The annual cost of defense for the model is 18% of the energy contained in the mean number of eggs produced. When the energy allocated to eggs is added to that allocated to defense, the model has an annual investiment that is greater than the annual investment in reproduction by the mimic. Although the energy invested in defense by the model is small relative to the energy invested in egg production, it buys the model considerable protection from predation. Nevertheless, the cost of defense does not explain the deviations from the predictions of life-history theory.     

Host feeding in insect parasitoids: why destructively feed upon a host that excretes an alternative?

Host feeding is the consumption of host tissue by the adult female parasitoid. We studied the function of destructive host feeding and its advantage over non‐destructive feeding on host‐derived honeydew in the whitefly parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae). We allowed parasitoids to oviposit until they attempted to host feed. We either prevented or allowed host feeding. Parasitoids had access to sucrose solution, with or without additional access to honeydew. Parasitoids that were allowed to host feed did not have a higher egg load 20 or 48 h after host feeding than parasitoids prevented from host feeding. Host feeding did not increase the number of eggs matured within these periods, nor did the time spent host feeding positively affect any of these response variables. On the other hand, the presence of honeydew did have a positive effect on egg load 20 and 48 h after host feeding compared with parasitoids deprived of honeydew. Parasitoids with access to honeydew matured more eggs within these periods than honeydew‐deprived parasitoids. Host feeding increased life expectancy, but this effect was nullified when honeydew was supplied after the host‐feeding attempt. In conclusion, feeding on honeydew could be an advantageous alternative to host feeding in terms of egg quantity and longevity. This applies especially to parasitoids exploiting Homoptera, because these parasitoids can obtain honeydew from the host itself. It is possible that destructive host feeding has evolved to enable females to sustain the production of high‐quality anhydropic eggs, which may be important in the parasitoid's natural environment. We argue that future studies should take natural alternative food sources into more consideration.     

Parasitoid size as a function of host sex: potential for different sex allocation strategies

Parasitoid females are known to preferentially allocate female eggs to hosts with the higher resource value, usually leading to oviposition of female eggs in larger hosts and male eggs in smaller hosts. For koinobiont parasitoids, if male and female hosts are of equal size at time of oviposition, but differ in size in later developmental stages, the sex of the host could be used to indicate future resource value. Using parasitoids of the braconid genus Asobara, which are larval parasitoids of Drosophila, it is shown that parasitoids emerging from female hosts are larger than those from male hosts. Given this difference in resource value, ovipositing females should preferentially allocate female eggs to female hosts. An alternative strategy would be to decrease the difference in resource value between male and female hosts by castrating male hosts. The primary sex ratio of A. tabida in their two main host species does not differ between male and female hosts. In contrast to A. tabida, A. citri is known to partially castrate male hosts, but this does not decrease the size difference between male and female hosts. As in A. tabida, there is no difference in sex allocation to male and female hosts in A. citri. Despite the clear difference between the resource value of male and female hosts, these parasitoid species do not seem to make optimal use of this difference. They may not be able to discriminate between host sexes or, alternatively, there is a presently unknown fitness disadvantage to ovipositing in female hosts.     

How to be a fig wasp down under: The diversity and structure of an Australian fig wasp community

Endophytic insects and their parasitoids provide valuable models for community ecology. The wasp communities in inflorescences of fig trees have great potential for comparative studies, but we must first describe individual communities. Here, we add to the few detailed studies of such communities by describing the one associated with Ficus rubiginosa in Australia. First, we describe community composition, using two different sampling procedures. Overall, we identified 14 species of non-pollinating fig wasp (NPFW) that fall into two size classes. Small wasps, including pollinators, gallers and their parasitoids, were more abundant than large wasps (both galler and parasitoid species). We show that in figs where wasps emerge naturally, the presence of large wasps may partly explain the low emergence of small wasps. During fig development, large gallers oviposit first, before and around the time of pollination, while parasitoids lay eggs after pollination. We further show that parasitoids in the subfamily Sycoryctinae, which comprise the majority of all individual NPFWs, segregate temporally by laying eggs at different stages of fig development. We discuss our results in terms of species co-existence and community structure and compare our findings to those from fig wasp communities on other continents.     

The costs of crest induction for Daphnia carinata

The effects of notonectid-induced crests on growth and reproduction, and resource allocation to crest construction, moult losses and eggs of Daphnia carinata were measured. An attempt was made to elucidate the mechanisms of physiological costs of crest induction for this species. The crested morph of d. carinata reached a significantly larger size than the uncrested form. Reproductive output was similar in early instars, but the crested morph produced more eggs in latter broods. Instar duration was longer for the crested morph and age at first reproduction was delayed. Survival was also lower in this form. Crest construction required significant resources (equivalent to 60 eggs over a life time) but evidence is presented that these resources were obtained primarily by re-allocation of available material rather than collection of extra resources. The crested morph allocated significantly more resources to moulting than its uncrested counter-parts. The uncrested morph produced large eggs in early instars and progressively smaller ones in later instars. The crested morph produced only small eggs. The hypothesis is presented that the crest-induction strategy of D. carinata involves at least two separate sets of responses, each with its own costs and trade-offs. The first response is production of the crest. The cost of crest production is an increased cost of moulting. D. carinata off sets this cost by increasing instar duration and thus age at reproduction. The second response is increased size. D. carinata achieves this by reducing the fraction of available resources allocated to reproduction. The cost is lower reproductive output.     

Delayed selfing in relation to the availability of a mating partner in the cestode Schistocephalus solidus

Abstract A hermaphroditic individual that prefers to outbreed but that has the potential of selfing faces a dilemma: in the absence of a partner, should it wait for one to arrive or should it produce offspring by selfing? Recent theory on this question suggests that the evolutionary solution is to find an optimal delay of reproduction that balances the potential benefit of outcrossing and the cost of delaying the onset of reproduction. Assuming that resources retained from breeding can be reallocated to future reproduction, isolated individuals, compared with individuals with available mates, are predicted to delay their age at first reproduction to wait for future outcrossing. Here, I present empirical support for this idea with experimental data from the hermaphroditic cestode Schistocephalus solidus. I show that individuals breeding alone delay their reproduction and initially produce their eggs at a slow rate relative to cestodes breeding in pairs. This delay is partly compensated for by a later higher egg production, although singly breeding cestodes still pay a cost of overall lower egg production.     

松毛虫卵期几种寄生蜂的共寄生现象及其对寄生率的影响

松毛虫赤眼蜂Ｔｒｉｃｈｏｇｒａｍｍａｄｅｎｄｒｏｌｉｍ　Ｍａｔｓｕｍｕｒａ,白跗平腹小蜂ＰｓｅｕｄａｎａｓｔａｔｕｓａｌｂｉｔａｒｓｉｓＡｓｈｍｅａｄ,松毛虫宽缘金小蜂Ｐａｃｈｙｎｅｕｒｏｎ　ｓｏｌｉｔａｒｉｕｍ（Ｈａｒｔｉｇ）,松毛虫黑卵蜂Ｔｅｌｅｎｏ－ｍｕｓ　ｄｅｎｄｒｏｌｉｍｕｓｉ　Ｃｈｕ和大蛾卵跳小蜂Ｏｏｅｎｃｙｒｔｕｓｋｕｗａｎａｅ（Ｈｏｗａｒｄ）是松毛虫卵期几种主要寄生蜂。通过对上述几种寄生蜂寄生习性的研究表明：赤眼蜂和平腹小蜂不但能寄生新鲜害虫卵,还可以寄生对方已寄生并已发育１—３天的寄生卵,但羽化率均不高;松毛虫宽缘金小峰不寄生新鲜害虫卵,专门寄生赤眼蜂寄生后已发育１—７天的寄生卵,其中又以赤眼蜂发育３—５天的卵寄生率和羽化率为最高。除赤眼蜂和平腹小蜂可以混合使用外,其它蜂种混用都不同程度地存在相互排挤的现象。如果先让平腹小蜂寄生尔后再让赤眼蜂寄生或先让赤眼蜂寄生,尔后再让跳小蜂或黑卵蜂寄生,能够提高卵块寄生率和充分发挥各自天敌的作用。