Adaptive superparasitism in solitary parasitoids: marking of parasitized hosts in relation to the pay-off from superparasitism

Abstract.

• 1 The pay-off from an egg laid in a parasitized host is an important parameter in models on adaptive superparasitism in solitary insect parasitoids.
• 2 For Leptopilina heterotoma, a parasitoid of larval Drosophila, the pay-off from a second egg laid in a host is 0.43 offspring when the interval between the two ovipositions is less than 3h. For longer intervals, this pay-off decreases to almost zero for an interval of 24 h.
• 3 When a female encountering a parasitized host is able to estimate the interval since the first oviposition, it is expected that she will take this into account in her host selection decisions. This is, however, not in the direct interest of the female that lays the first egg, and marks the host.
• 4 We studied whether superparasitism in hosts containing a young egg is more common than in hosts containing an older egg, when searching in a patch containing once-parasitized and unparasitized hosts.
• 5 The acceptance/encounter ratio of parasitized hosts increased for intervals longer than 6h, as predicted when the interests of the marking female and the longevity of the mark are taken into account.
• 6 Superparasitism occurred more often when parasitoids had previously searched a host patch 7 days before the experiment compared to when parasitoids had searched a patch 1 day before, a phenomenon predicted by dynamic optimal diet models.

     

Asymmetric larval competition between two species of solitary parasitoid wasps: the influence of superparasitism

Abstract.

• 1 We test the hypothesis that a solitary parasitoid wasp may gain in fitness if she lays more eggs in a host.
• 2 Using heterospecific superparasitism (=multiparasitism) between the solitary aphid parasitoids, Aphidius smithi Sharma & Subba Rao and Ephedrus californicus Baker, we show that (i) a superparasitizing female's chance that her offspring will survive competition is an increasing function of egg density, and (ii) survival among same-aged larvae is independent of the oviposition sequence.
• 3 These findings on asymmetric larval competition provide indirect evidence that supports two fundamental, but untested, assumptions underlying models of adaptive superparasitism between conspecific wasps.

     

Oviposition decisions in an endoparasitoid under self-superparasitism conditions

Superparasitism is a widespread phenomenon. Having accepted superparasitism, mated female parasitoids must decide on the sex of each egg they subsequently lay into the same host. Theory predicts that this decision is either based on host quality, when more male eggs are laid in hosts that are already parasitized because they are perceived to be of poorer quality; or more eggs are laid of the sex that is most likely to be a strong larval competitor, i.e. generally females.Anastatus disparis is a facultative endoparasitic egg parasitoid. We used ‘artificial’ hosts to explore outcomes of decision making by A. disparis during superparasitism under a manipulated absence of larval competition. When only one egg was laid it was always female. As the number of eggs laid increased, so more of them were male. This supports the theory that oviposition decisions are based on host quality; more male eggs were laid in hosts that were already parasitized and thus of poorer quality.In a second experiment, eggs were exposed to parasitoids for different periods of time. Half the eggs were dissected to determine the number of parasitoid eggs that had been laid. The remaining eggs were incubated and the number and sex of offspring that ultimately emerged, following larval competition, were recorded. Under superparasitism conditions fierce larval competition ensued; only one offspring survived and they were predominantly female.In conclusion, oviposition decisions by female A. disparis accepting self-superparasitism were made based on host quality.     

Co‐foundress confinement elicits kinship effects in a naturally sub‐social parasitoid

Kinship among interacting individuals is often associated with sociality and also with sex ratio effects. Parasitoids in the bethylid genus Goniozus are sub‐social, with single foundress females exhibiting post‐ovipositional maternal care via short‐term aggressive host and brood defence against conspecific females. Due to local mate competition (LMC) and broods normally being produced by a single foundress, sex ratios are female‐biased. Contests between adult females are, however, not normally fatal, and aggression is reduced when competing females are kin, raising the possibility of multi‐foundress reproduction on some hosts. Here, we screen for further life‐history effects of kinship by varying the numbers and relatedness of foundresses confined together with a host resource and also by varying the size of host. We confined groups of 1–8 Goniozus nephantidis females together with a host for 5+ days. Multi‐foundress groups were either all siblings or all nonsiblings. Our chief expectations included that competition for resources would be more intense among larger foundress groups but diminished by both larger host size and closer foundress relatedness, affecting both foundress mortality and reproductive output. From classical LMC theory, we expected that offspring group sex ratios would be less female‐biased when there were more foundresses, and from extended LMC theory, we expected that sex ratios would be more female‐biased when foundresses were close kin. We found that confinement led to the death of some females (11% overall) but only when host resources were most limiting. Mortality of foundresses was less common when foundresses were siblings. Developmental mortality among offspring was considerably higher in multi‐foundress clutches but was unaffected by foundress relatedness. Groups of sibling foundresses collectively produced similar numbers of offspring to nonsibling groups. There was little advantage for individual females to reproduce in multi‐foundress groups: single foundresses suppressed even the largest hosts presented and had the highest per capita production of adult offspring. Despite single foundress reproduction being the norm, G. nephantidis females in multi‐foundress groups appear to attune sex allocation according to both foundress number and foundress relatedness: broods produced by sibling foundresses had sex ratios similar to broods produced by single foundresses (ca. 11% males), whereas the sex ratios of broods produced by nonsibling females were approximately 20% higher and broadly increased with foundress number. We conclude that relatedness and host size may combine to reduce selection against communal reproduction on hosts and that, unlike other studied parasitoids, G. nephantidis sex ratios conform to predictions of both classical and extended LMC theories.     

Primary sex-ratio and differential progeny survivorship in solitary haplo-diploid parasitoids

ABSTRACT.

• 1 A method of partitioning emergence sex-ratio to give estimates of primary sex-ratio and male and female offspring survival from oviposition to emergence in solitary haplo-diploid parasitoids is presented.
• 2 This method is applied to sex-ratio data from a larval parasitoid, Aphidius ervi Haliday, and a pupal parasitoid, Coccygomimus turionella L., parasitizing a range of host types.
• 3 There was no evidence of facultative control of primary sex-ratio in either species. Parasitoid emergence sex-ratios were similar for all host sizes attacked by C. turionella. In contrast, emergence sex-ratios of A.ervi showed a significant male bias in smaller hosts. This shift in emergence sex-ratio was attributable to differential progeny survival.
• 4 Pre-emergence mortality in both species was a function of host size, with few offspring surviving from small hosts. This suggests that host size may be an important component in the dynamics of host-parasitoid interactions.
• 5 The evolution of sex-ratio regulatory mechanisms in solitary haplo-diploid parasitoids is discussed in the context of parasitoid life-history. We suggest that there is a constraint to the evolution of the facultative control of primary sex-ratio in parasitoids attacking larval stages as a result of the uncertainty of future host resource acquisition rates.

     

Superparasitism of larval hosts by the walnut fly, <Emphasis Type="Italic">Rhagoletis juglandis</Emphasis>, and its implications for female and offspring performance

The oviposition-preference–offspring-performance hypothesis predicts that female insects should prefer to deposit clutches on or in hosts that maximize offspring performance. An important assumption behind this prediction is that female fitness is tightly correlated with the fitness of any one offspring. In this study, we evaluate offspring performance in the walnut fly, Rhagoletis juglandis Cresson (Diptera: Tephritidae), in relation to a previously described oviposition preference for previously exploited host fruit. In particular, we examined how superparasitism of walnut hosts influences offspring survival and weight at pupation under field conditions. We found that superparasitism was common and that increases in larval densities within fruit were associated with reduced larval survival and weight at pupation. In a laboratory experiment, female size was correlated with lifetime fecundity. In this system, oviposition preference is therefore negatively, not positively, correlated with offspring performance. We argue that patterns of female preference in this system reflect direct benefits to females that are traded off against costs in terms of offspring fitness. Because female fitness is a product not only of offspring quality but also of the total number of offspring produced, female walnut flies may be optimizing their fitness by producing many less fecund offspring. Studies examining the preference-performance hypothesis should consider the reproductive conflicts between parents and offspring as potential factors that influence the congruence between parental preference and offspring performance.     

Costs and consequences of superparasitism in the polyembryonic parasitoid Copidosoma koehleri (Hymenoptera: Encyrtidae)

Abstract.  1. Polyembryonic wasps provide dramatic examples of intra-specific developmental conflict. In these parasitoids, each egg proliferates into a clonal lineage of genetically identical larvae. If more than one egg is laid in a host (superparasitism), individuals of different clones may compete for food resources.
2. In the polyembryonic encyrtid Copidosoma koehleri , one larva per clone can differentiate into a sterile soldier. It is shown that soldiers are always females, and that they attack intra-specific competitors.
3. Research hypotheses were that (a) clones that develop in superparasitised hosts suffer heavier mortality than clones that develop in singly parasitised hosts, and (b) female clones cause higher mortality to their competitors than male clones, hence larval survival is lower in superparasitised hosts that contain females than in male-only broods.
4. The potential frequency of superparasitism in C. koehleri was manipulated by varying parasitoid–host ratios and exposure durations.
5. As parasitoid densities and exposure durations increased, the frequency of superparasitism rose, brood sizes increased, but the number of hosts that completed development was reduced. The number of offspring per parasitoid female decreased with increasing parasitoid–host ratios. Offspring size and longevity were inversely correlated with brood size. As superparasitism rates increased, fewer all-male broods were produced. Male–female broods were female-biased, suggesting selective killing of males by female soldiers. All-female broods were significantly smaller than all-male broods at high parasitoid densities only, possibly reflecting aggression among soldiers of competing clones.
6. The results support the working hypotheses, and suggest that female larvae outcompete males in superparasitised hosts.     

寄主大小及寄生顺序对蝇蛹佣小蜂寄生策略的影响

寄主大小模型认为寄生蜂后代性比与寄主大小相关,寄生蜂倾向于在大寄主上产出更多雌性后代,在小寄主上产出更多雄性后代.探讨了以家蝇蛹为寄主时,蝇蛹佣小蜂后代产量和性比变化;单次寄生情况下,寄主大小及寄生顺序对寄生蜂后代性比等影响.结果表明,蝇蛹佣小蜂的产卵期为(8.93±3.34)d,单头雌蜂能产雌性后代(34.11±16.34)头和雄性后代(11.04±8.87)头,且雄性百分比为0.24±0.11.随成蜂日龄的增大,寄生蜂产生雄性后代的比率显著增加.蝇蛹佣小蜂在寄生家蝇蛹时,会优先选择寄生个体较大的蛹;在单次寄生的情况下,蝇蛹佣小蜂倾向于在较大的家蝇蛹内产出更多的雌性后代.     

Brood sex ratio variance,developmental mortality and virginity in a gregarious parasitoid wasp

Females of the parasitoid wasp Goniozus nephantidis paralyse host caterpillars and lay a clutch of up to 18 eggs onto the host integument. The known biology of G. nephantidis suggests that matings occur exclusively between siblings from the same brood. This leads to the prediction that brood sex ratios should be highly female-biased and have low variance. Sex ratios are indeed female-biased, with the mean proportion of males equal to 0.093. However, while sex ratio variance is significantly less than binomial, many broods contain no males at emergence. During development 28% of G. nephantidis offspring die. Male mortality offers a potential explanation for all-female (= virgin) broods. For the clutch sizes and mortality observed, theory predicts that <10% of females will emerge from all-female broods but the empirical value is much higher. The prediction that the prevalence of virginity decreases with increasing clutch size is, however, supported. We consider alternative explanations for the observed proportion of all-female broods, but this appears to be neither an artefact of the laboratory environment nor due to incorrect assumptions about G. nephantidis life history. Although its reproductive biology has been much investigated and its sex ratio matches some theoretical predictions, we conclude that a fuller understanding of G. nephantidis sex ratio requires a deeper knowledge of its field biology.     

Presence of a conspecific increases superparasitism but not infanticide under self‐ and conspecific superparasitism in a semisolitary parasitoid,Echthrodelphax fairchildii (Hymenoptera: Dryinidae)

Female parasitoids are expected to avoid superparasitism (ovipositing in and/or on parasitized hosts) when unparasitized hosts are available. However, when the supply of unparasitized hosts is restricted, they are expected to self‐ as well as conspecifically superparasitize. One of the cues of a reduced availability of unparasitized hosts is the presence of a conspecific. Moreover, if the focal species can perform infanticide, after encountering a conspecific female, the females are expected to kill eggs existing in and/or on hosts when superparasitizing, because the eggs are more likely to be laid by others. In this study we investigated whether females of an infanticidal semisolitary parasitoid, Echthrodelphax fairchildii, increase their frequencies of superparasitism and infanticide after encountering a conspecific female. Echthrodelphax fairchildii females are capable of discriminating between self‐ and conspecific superparasitism until up to 0.75 h after the first egg was laid (self‐superparasitism frequency < conspecific superparasitism frequency). As expected, the female parasitoids were more likely to perform self‐ and conspecific superparasitism after they had encountered a conspecific. In particular, the self‐superparasitism frequency increased highly within a short period after the first oviposition, so that no difference between the self‐ and conspecific superparasitism frequencies was found. In contrast, the infanticidal‐probing frequency remained extremely low, irrespective of whether or not the female parasitoids had encountered a conspecific. Moreover, when superparasitizing, females usually laid female eggs. Possible causes for the low frequency of infanticidal probing and the female‐biased sex ratio are discussed.     

RETRACTED ARTICLE: Foraging of Host-Habitat and Superparasitism in <Emphasis Type="Italic">Cotesia glomerata</Emphasis>: A Gregarious Parasitoid of <Emphasis Type="Italic">Pieris brassicae</Emphasis>

The study investigates differences in the oviposition pattern of a braconid parasitoid, Cotesia glomerata (Linn.) in Pieris brassicae (Linn.) in relation to their use of different cruciferous food plants. The response of P. brassicae to superparasitism and consequences for the parasitoid were examined in order to elucidate the ecological significance of this behaviour. Female parasitoid located various crucifers and searched for host more frequently almost on all the host plants tested i.e. cabbage, cauliflower, Chinese cabbage, broccoli and radish. According to the estimated relative number of female locating hosts, cabbage was the most attractive plant for C. glomerata and total number of eggs laid in host larvae feeding on it was higher than in larvae feeding on other plants. Laboratory experiments demonstrated that superparasitism reduced survivorship of P. brassicae larvae. Superparasitism lengthened parasitoid development and prolonged the feeding period of host larvae. Sex ratio and the body weight of emergent wasps correlated negatively with brood size. Despite a trade-off between maximising brood size and optimising the fitness of individual offspring, two or three ovipositions on P. brassicae larvae resulted in a greater female dry mass than did a single oviposition on the host. Thus, superparasitism might be of adaptive significance under certain circumstances, especially when host density is low and unparasitized hosts are rare in a habitat.     

The effect of superparasitism on development of the solitary parasitoid wasp, Venturia canescens (Hymenoptera: Ichneumonidae)

Abstract.

• 1 The effects of superparasitism on the rate of development, adult size and mortality of Venturia canescens (Hymenoptera: Ichneumonidae) were investigated. Parasitoids were reared from third (L3) and fifth (L5) instars of one of its hosts, Plodia interpunctella (Lepidoptera: Pyralidae) containing one, two or four parasitoid eggs.
• 2 Superparasitism increased the development time of Venturia reared from both instars, but the developmental delay was more evident in wasps from L5 hosts.
• 3 The size of parasitoids from L3 hosts was unaffected by egg number, but wasps from both superparasitized L5 treatments were significantly smaller than those from singly parasitized hosts.
• 4 Parasitoid mortality was significantly higher in L5 than L3, but within instars did not differ significantly with egg number.
• 5 The results confirm that superparasitism may affect the fitness of both the adult female wasp and her progeny, and should therefore be incorporated into models of superparasitism as an adaptive foraging strategy.

     

Superparasitism and mutual interference in the egg parasitoid Anagrus delicatus (Hymenoptera: Mymaridae)

Abstract.

• 1 In nature, interference among Anagrus delicatus (Hymenoptera: Mymaridae) parasitoids reduced the per-capita number of hosts parasitized. Interference increased with parasitoid density.
• 2 Anagrus delicatus did not avoid parasitizing hosts that had recently been parasitized by conspecific wasps. Evidence indicated that this superparasitism was largely a random process, increasing with the ratio of parasitized to unparasitized hosts.
• 3 Individual parasitoid efficiency, the number of hosts killed per wasp per unit time, decreased with increasing wasp density. This occurred whether wasps searched the patch together (simultaneously) or one by one (sequentially), and was the result of an increase in time spent superparasitizing hosts at higher wasp density. This is known as indirect mutual interference.
• 4 Increasing numbers of parasitoids together on the same patch caused a significant decline in the rate and per-capita number of hosts parasitized. However, there was not a correspondent decline in searching efficiency with increasing wasp density (i.e. no direct mutual interference).
• 5 These forms of parasitoid density dependence should contribute to the stability of the host—parasitoid interaction.

     

Adaptive significance of facultative infanticide in the semi-solitary parasitoid Echthrodelphax fairchildii

Abstract.  1. This is the first work to show how imperfect kin recognition influences the behavioural strategy of parasitoids.
2. The female of Echthrodelphax fairchildii lays an egg on the right or left side of the host thorax. When superparasitising on the side without the first offspring, it often probed the opposite side with its sting and killed the first offspring more than 50% of the time. The frequency of probing increased with increasing inter-oviposition interval, and was higher in conspecific superparasitism than in self superparasitism.
3. The adaptiveness of probing was assessed by the difference in fitness returns between superparasitism with probing and superparasitism without probing. Fitness returns from self‐superparasitism and those from conspecific superparasitism were assessed by the fitness performance of both first and second comers, and that of second comers respectively.
4. In terms of the survival rate of immatures (one fitness component), probing under conspecific superparasitism guaranteed higher fitness returns than not probing for longer oviposition intervals, but under self‐superparasitism not probing guaranteed higher fitness returns for shorter intervals because superparasitism for such intervals often resulted in two-adult emergence.
5. In terms of head width (another fitness component), probing produced higher fitness returns for shorter oviposition intervals for both self and conspecific superparasitism.
6. Assuming that offspring quantity contributes more to fitness returns than does offspring quality, the observed frequencies of probing were considered adaptive for parasitoids whose abilities to distinguish between self and conspecifically parasitised hosts and to estimate inter-oviposition intervals are imperfect.     

Parasitisation of Tetrastichus brontispae (Hymenoptera: Eulophidae), a biological control agent of the coconut hispine beetle Brontispa longissima (Coleoptera: Chrysomelidae)

The gregarious endoparasitoids Tetrastichus brontispae Ferrière is one of the important natural enemies of the coconut hispine beetle Brontispa longissima (Gestro), a serious invasive pest on coconut palm plants (Cocos nucifera L.) in Southeast Asia. Development at different temperatures, effect of host and female ages, effect of food and oviposition frequency and superparasitism were investigated in the laboratory. Females were allowed only one attack against one host in all experiments. The wasp developed in a host between 19 and 30°C, whilst no wasp completed its immature development at 16 and 31°C. Host and female ages affected parasitisation. Parasitoid emergence was high on day 0 and day 1 pupal hosts, and younger females produced more offspring than older females. The longevity of the female was affected not only by food supply, but also by oviposition frequency. The female survived longer when oviposition frequency was low. However, the total number of hosts parasitised by the female during her lifetime did not differ at different oviposition frequencies. In superparasitism, although the percentage of adult emergence and body size of offspring decreased with an increasing number of attacks per host, a host parasitised by up to four females could produce parasitoid offspring.     

Self-/conspecific discrimination and superparasitism strategy in the ovicidal parasitoid Echthrodelphax fairchildii （Hymenoptera： Dryinidae）

Superparasitism in solitary parasitoids results in fatal competition between the immature parasitoids, and consequently only one individual can emerge. In the semisoli- tary ovicidal parasitoid Echthrodelphaxfairchildii （Hymenoptera： Dryinidae）, 2 adults can emerge under superparasitism with a short interval （〈24 h） between the first and second ovipositions. We determined the female parasitoid＇s behavioral responses under self- and conspecific superparasitism bouts with first-to-second oviposition intervals of 〈2 h. The self- and conspecific superparasitizing frequencies increased up to an oviposition interval of 0.75 h, with the former remaining lower than the latter, particularly for oviposition intervals of _〈0.25 h, suggesting the existence of self-/conspecific discrimination. The superparasitizing frequency plateaued for oviposition intervals of _〉0.75 h, with no dif- ference between self- and conspecific superparasitism. The ovicidal-probing frequency did not differ under self- and conspecific superparasitism, and was usually 〈20%. The females exhibited no preference for the oviposition side （i.e., ovipositing on the side with or without the first progeny） and almost always laid female eggs for any oviposition in- terval under self- and conspecific superparasitism. The sex ratio was not affected by the type of superparasitism, oviposition sides, or the occurrence of ovicidal probing. These observed results about the oviposition side, ovicidal probing, and sex ratios differed from the predictions obtained assuming that the females behave optimally. Possible reasons for the discrepancies are discussed： likely candidates include the high cost of selecting oviposition sides and ovicidal probing, and, for the sex ratio, the low frequency of encountering suitable hosts before superparasitism bouts.     

Reproductive and subsocial behaviour in the ovoviviparous leaf beetle Gonioctena sibirica (Coleoptera: Chrysomelidae)

Abstract.

• 1 In the spring, females of the leaf beetle Gonioctena sibirica deposited larvae on the ventral surface of growing young leaves situated on the apical position of shoots of the willow Salix bakko.
• 2 The parent females remained with the larvae usually on the underside of the basal part of leaves, facing toward the base of shoots. When other arthropods approached, the females temporarily moved towards these intruders, showing aggressive behaviour such as swinging the body or stamping the legs. Many females remained with their larvae until the larvae grew into the final (fourth) instar. No female produced an additional brood in the field.
• 3 Broods from which parent females were experimentally removed suffered higher mortality than those in which females were left intact. Arthropods such as spiders and ants were observed preying on the larvae. In contrast, the survivorship of broods from which females were removed and intruders were excluded with a sticky substance applied to the base of twigs was not different from that of control broods. These results demonstrate that the main mortality factor of offspring is pedestrian arthropod predators and females physically repel the predators.
• 4 Potentially alternative reproductive strategies, such as producing a large number of offspring by iteroparity and/or larger brood(s) with less or no care, seem to be inhibited in G.sibirica by larval dependence on growing young leaves which are temporally limited and by ovoviviparity which may have limited brood size.

     

Local Mating,Dispersal and Sex Ratio in a Gregarious Parasitoid Wasp

Parasitoid sex ratios can be greatly influenced by mating and dispersal behaviour. Many sex ratio models assume that mating is strictly local (only mated females disperse from the natal patch) and that a single male is sufficient to inseminate all females in a brood. Bethylids (aculeate parasitoids) have been used to test predictions of these models, but less attention has been paid to testing their underlying assumptions. We investigated the timing of eclosion, mating and dispersal in mixed-sex and single-sex broods of the bethylid wasp Goniozus nephantidis. In mixed-sex broods, almost all females mate before dispersal and a single male is sufficient to inseminate virtually all females, even when brood sizes are large. Males disperse from both mixed-sex and all-male broods, but males in all-male broods disperse more slowly. Virgin females disperse from all-female broods, which are common. Virgin females can produce a brood, mate with their own sons and subsequently produce mixed-sex broods, but their success rate is very low. Virgin females could potentially circumvent sex allocation constraints by superparasitizing mixed-sex broods, but when presented with hosts bearing mixed-sex broods they destroy all members of the initial brood before ovipositing. Because of the high prevalence of single-sex broods and dispersal of both sexes, the mating structure of G. nephantidis is unlikely to conform to the assumption of strict local mating.     

Does mother really know best? Oviposition preference reduces reproductive performance in the generalist parasitoid Aphidius ervi

The reproductive success of female parasitoids is dependent on their ability to accurately assess the suitability of a host for larval development. For generalist parasitoids, which utilize a broad range of species and instars as hosts, a set of assessment criteria determines whether a host is accepted or rejected. The suitability of a host, however, can only be imperfectly assessed by the female parasitoid, which can result in the selection of lesser quality hosts for oviposition. In this study we explored the disparity between host quality and host preference using the generalist koinobiotic parasitoid Aphidius ervi Haliday (Hymenoptera: Aphidiidae) and the host Aulacorthum solani (Harris) (Homoptera: Aphididae), the foxglove aphid. The second instar hosts produced the highest level of reproductive success, while third and fourth instars resulted in a substantially reduced reproductive performance. When given a choice of host instars, parasitoids preferred the older hosts for oviposition disregarding their reduced suitability for larval development. Results are discussed in context of mechanisms involved in A. ervi host selection and biases in the criteria used to assess hosts that may arise when parasitoids transfer host species between generations.     

Imperfect preference for singly parasitized hosts over doubly parasitized hosts in the semisolitary parasitoid Echthrodelphax fairchildii: implications for profitable self-superparasitism

Self‐superparasitism can be profitable (i.e., a fitness gain) when conspecific female adult parasitoids prefer singly parasitized hosts over doubly parasitized hosts. This preference is expected to evolve when the value (i.e., the fitness gain from oviposition) of doubly parasitized hosts is lower than that of singly parasitized hosts. We examined whether such a preference is found in the small brown planthopper, Laodelphax striatellus (Fallén) (Homoptera: Delphacidae), and its semisolitary infanticidal parasitoid Echthrodelphax fairchildii Perkins (Hymenoptera: Dryinidae). We compared the preferences and host values between each of four pairs of double and triple parasitism, each of which had the same time interval between the first and last oviposition bouts. Ovipositions on doubly and singly parasitized hosts occurred with similar frequencies in each of the four pairs, even though the doubly parasitized hosts were of lower value than the singly parasitized hosts. However, the value of doubly parasitized hosts with the first and second parasitoid offspring on the same side of the host was higher than that of hosts with the two offspring on different sides, and the value of the former did not differ significantly from that of singly parasitized hosts. The preferences between singly and doubly parasitized hosts with the two offspring on the same or different sides were as expected from differences in their values, except for one pair of double and triple parasitisms. This exception is considered attributable to an imperfect ability to evaluate hosts.