Infanticide in a Dryinid Parasitoid, Haplogonatopus atratus

When a parasitized host is superparasitized, the second comer—an immature parasitoid originating from the second oviposition—is usually handicapped relative to the first comer in the competition for the host. In Haplogonatopus atratus, however, the survival rate of second comers is frequently higher than that of first comers. Infanticide is assumed to be responsible for this phenomenon. The present report reveals that, when the female wasp of H. atratus superparasitizes, she examines several membranes between the host's abdominal terga with her stinger before laying a supernumerary egg and that, when she locates the first comer, she pierces it with her stinger to kill it. Moreover, once she catches a host she performs infanticide irrespective of whether the host is self- or conspecifically parasitized.     

Environmental and genetic determinants of ovicide in parasitic wasp Bracon hebetor

Superparasitism occurs when a parasitoid lays a second clutchof eggs on a host previously parasitised by herself or a conspecific.Ovicide refers to a parasitoid destroying an existing clutchof eggs on a parasitized host before laying a second clutch.We investigated environmental and genetic determinants of ovicidein the parasitic wasp Bracon hebstor. Characterization of egglayingbehavior revealed that B. hebetor commits ovicide during thehost examination phase of oviposition. The temporal costs ofovicide were found to be relatively small for females that experiencedlow rates of host encounter, whereas the costs of ovicide increasedfor females that experienced a high rate of host encounter.Individual wasps committed ovicide on conspecifically parasitizedhosts more frequently than on self-parasitized hosts. Manipulationexperiments suggested that B. hebetor females learn about theirenvironment while foraging and commit ovicide on the basis ofthe travel time between successive hosts. Significant differenceswere also found in ovicidal behavior among laboratory and fieldpopulations of B. hebetor. The implications of our results forclutch size theory and the evolution of ovicide are discussed.     

Seemingly maladaptive refraining from infanticidal probing at the third parasitism attack by the semi-solitary parasitoid Echthrodelphax fairchildii （Hymenoptera： Dryinidae）

We assessed the adaptiveness of refraining from infanticidal probing at the third attack under triple parasitism in the parasitoid Echthrodelphaxfairchildii Perkins, by comparing fitness returns from the third attack with and without probing. Fitness returns were assessed in terms of the survival rate, mean developmental time, and mean adult head width of the progenies. Not probing was maladaptive under triple parasitism with oviposition intervals of 1/24 and 24/24 hours （where the numbers before and after the slash refer to the first-to-second and second-to-third oviposition intervals, respectively）, although no significant difference was detected in fitness returns for oviposition intervals of 24/1 hours. We suggest that the cost of probing （especially the decrease in the chance of future ovipositions） is a reason for the seemingly maladaptive absence of probing.     

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.     

Fitness consequences of ovicide in a parasitoid wasp

Ovicide, superparasitism and host rejection are alternative reproductive tactics facing female parasitoid wasps encountering an already-parasitized host. Superparasitism is simply the addition of an egg or a clutch of eggs by the secondary parasitoid, but under ovicide the primary clutch is removed or destroyed. Host rejection occurs if the wasp leaves without laying a clutch. The ectoparasitoid Laelius pedatus (Say) (Hymenoptera: Bethylidae) performs ovicide in this situation. Clutch manipulation experiments show that secondary clutches suffer high mortality in competition with primary clutches, which increases with increasing time delay between clutches. Primary clutches however suffer little in competition with secondary clutches, even if there is minimal time delay between clutches. These data suggest that the offspring of ovicidal females are substantially fitter than the offspring of superparasitizing females. Handling time and clutch size do not differ significantly between first (sole) parasitoids and second (ovicidal) parasitoids. The same is true for offspring survival and development time. However, offspring of second females are slightly smaller. This suggests that parasitized and unparasitized hosts are resources of similar quality when ovicide is performed. These data strongly support the predictions of evolutionary models of ovicide. They may also give some insight into the taxonomic distribution of ovicide in parasitoids.     

拟寄生昆虫中的过寄生现象

对拟寄生昆虫同种过寄生现象做了综述。拟寄生昆虫的认识能力和寄生经历、其与寄主数量的相对比例、寄主的大小及两次被寄生的时间间隔等是导致过寄生是否出现的主要因素。过寄生常导致拟寄生昆虫发育历期延长、存活率下降、个体变小、子代雌性比降低。试验研究和大量饲养中应采取措施避免过寄生。     

Thief ants have reduced quantities of cuticular compounds in a ponerine ant, Ectatomma ruidum

Abstract. Workers of a tropical ponerine ant, Ectatomma ruidum (Roger), exhibit a system of intercolonial thievery for food; thief ants enter conspecific colonies, intercept food, and carry it to their own colony. We analysed thief ants, ants from the thief's colony, and ants from the colony being robbed to determine if changes in cuticular profiles could facilitate entry by thieves into a target colony. Thief ants have significantly lower total quantities of dichloromethane-soluble cuticular compounds than non-thieves. The reduction in cuticular compounds on thieves suggests that thievery is facilitated by inhibition of either synthesis or acquisition of its home colony's recognition cues. Five of the fifteen compounds differed significantly in their relative proportion among colonies. Principal components analysis lends support to the hypothesis that both inhibition of a thief's home colony cues and acquisition of its target colony's cues play a role in successful thievery.     

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.     

Selection Strategies of Parasitized Hosts in a Generalist Parasitoid Depend on Patch Quality but Also on Host Size

Host rejection, superparasitism, and ovicide are three possible host selection strategies that parasitoid females can adopt when they encounter parasitized hosts. These differ in costs (in terms of time and energy required) and benefits (in terms of number and quality of offspring produced). Their relative payoff should vary with patch quality, (i.e., proportion of parasitized hosts present), and female choice between them should be adapted accordingly. We conducted behavioral observations to test the effect of the ratio of parasitized/unparasitized hosts present in a patch on the host selection strategies of Pachycrepoideus vindemmiae Rondani (Hymenoptera: Pteromalidae). This species being a generalist known to attack hosts of a great range of size, we also tested the impact of host size on female decisions with two host species differing greatly in size (Drosophila melanogaster and Delia radicum). We evaluated the adaptive value of each strategy in relation to host parasitization status and host size by measuring their duration and the potential number of offspring produced.     

单爪螯蜂属四新种（膜翅目：螯蜂科）

报道中国单爪螯蜂属Ａｎｔｅｏｎ Ｊｕｒｉｎｅ４新种,即平头单爪螯蜂Ａ．ｐｌａｎｕｍ,ｓｐ．ｎｏｖ．;横单爪螯蜂Ａ．ｔｒａｎｓｖｅｒｕｍ,ｓｐ．ｎｏｖ,齿单爪螯蜂Ａ．ｓｅｒｒａｔｕｍ,ｓｐ,ｎｏｖ．和凸单爪螯蜂Ａ．ｃｏｎｖｅｘｕｍ,ｓｐ,ｎｏｖ．模式标本保存于浙江大学。