Phenoloxidase in larvae of Plodia interpunctella (Lepidoptera: Pyralidae): molecular cloning of the proenzyme cDNA and enzyme activity in larvae paralyzed and parasitized by Habrobracon hebetor (Hymenoptera: Braconidae)

Phenoloxidase (PO) is a major component of the insect immune system. The enzyme is involved in encapsulation and melanization processes as well as wound healing and cuticle sclerotization. PO is present as an inactive proenzyme, prophenoloxidase (PPO), which is activated via a protease cascade. In this study, we have cloned a full-length PPO1 cDNA and a partial PPO2 cDNA from the Indianmeal moth, Plodia interpunctella (Hubner) (Lepidoptera: Pyralidae) and documented changes in PO activity in larvae paralyzed and parasitized by the ectoparasitoid Habrobracon hebetor (Say) (Hymenoptera: Braconidae). The cDNA for PPO1 is 2,748 bp and encodes a protein of 681 amino acids with a calculated molecular weight of 78,328 and pI of 6.41 containing a conserved proteolytic cleavage site found in other PPOs. P. interpunctella PPO1 ranges from 71-78% identical to other known lepidopteran PPO-1 sequences. Percent identity decreases as comparisons are made to PPO-1 of more divergent species in the orders Diptera (Aa-48; As-49; and Sb-60%) and Coleoptera (Tm-58; Hd-50%). Paralyzation of host larvae of P. interpunctella by the idiobiont H. hebetor results in an increase in phenoloxidase activity in host hemolymph, a process that may protect the host from microbial infection during self-provisioning by this wasp. Subsequent parasitization by H. hebetor larvae causes a decrease in hemolymph PO activity, which suggests that the larval parasitoid may be secreting an immunosuppressant into the host larva during feeding.     

Taxonomic notes on the genus Holepyris (Hymenoptera: Bethylidae) from Korea with descriptions of six new species

Six new species of the genus Holepyris (Hymenoptera: Bethylidae: Epyrinae) from Korea are described: H. brevicarinatus sp. nov., H. crinitus sp. nov., H. dimidiatus sp. nov., H. longicephalus sp. nov., H. mucro sp. nov. and H. multo sp. nov. They are described with illustrations of male genitalia and the biometric measurement data. A key to the Korean species of Holepyris based on males is provided.     

Bethylids attacking stored‐product pests: an overview

Bethylidae is a family belonging to the insect order Hymenoptera and contains about 2 200 described species. Bethylids typically parasitize larvae of Lepidoptera and Coleoptera, including species that are serious pests of stored products. Here, we review the main characteristics of each of the bethylids reported as biological control agent of these pests. The biological characteristics and peculiarities are reported for each species, and the potential for their practical application is discussed.     

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.     

Disruption of pupariation and eclosion behavior in the flesh fly, Sarcophaga bullata Parker (Diptera: Sarcophagidae), by venom from the ectoparasitic wasp Nasonia vitripennis (Walker) (Hymenoptera: Pteromalidae)

The action of venom from the ectoparasitic wasp, Nasonia vitripennis, was monitored by examining alterations in patterned muscular movements characteristic of pupariation and eclosion behavior in the flesh fly, Sarcophaga bullata. Venom injected into larvae prior to pupariation caused a dose-dependent delay in pupariation. Eventually, such larvae did pupariate, but puparia were abnormally formed. Barographic records revealed that all elements of pupariation behavior were present in venom-injected larvae, but pupariation behavior was not well synchronized with tanning, thus implying that the venom caused disruption in the temporal organization of central motor programs. When larvae were ligated and injected with venom posterior to the ligature, no response was evident in the posterior region, suggesting that the venom does not directly stimulate muscles or neuromuscular junctions. Injection of exogenous ecdysteroid into venom-injected larvae restored some elements of pupariation behavior, consistent with ecdysone's role in stimulating the release of anterior retraction factor and puparium tanning factor, two factors that are released from the CNS to regulate pupariation. When the venom was injected into newly emerged imagoes, the duration of extrication behavior was shortened, whereas all phases of post-eclosion behavior were lengthened. These observations imply that the venom affects CNS centers that regulate the muscular systems engaged in extrication and post-eclosion behavior.     

Competition for hosts between two hyperparasitoids of aphids,Dendrocerus laticeps andDendrocerus carpenteri (Hymenoptera: Megaspilidae): The benefit of interspecific host discrimination

The two hyperparasitoids of aphids, Dendrocerus carpenteri(Curtis) and Dendrocerus laticeps(Hedicke), differ in their interspecific host discrimination behavior: D. carpenterireadily accepts hosts for oviposition previously parasitized by D. laticeps,whereas D. laticepsoften refrains from ovipositing on hosts previously parasitized by D. carpenteri.The two species also differ in their competitive abilities: D. carpenteriis competitively superior to D. laticepswhen the time between ovipositions is 1 h. D. carpenteri's superiority probably arises from (a) the action of the venom produced by the female to paralyze the host, as evidenced by the comparison of emergence patterns from naturally vs artificially parasitized hosts, and (b) its more rapid egg development. Because of its competitive abilities, D. carpenterigains only limited benefit from discriminating interspecifically, at least when encountering a host parasitized by a competitively inferior species, such as D. laticeps.In contrast, D. laticepsgains considerable benefit from recognizing hosts previously parasitized by D. carpenteri,as the probability to produce offspring from such hosts is greatly reduced.     

Sex-allocation behaviour of a solitary ectoparasitoid: effects of host-patch characteristics and female density

The sex-allocation behaviour of the solitary ectoparasitoid Dinarmus basalis (Hymenoptera: Pteromalidae) was investigated by examining the female's response to two proximal factors: the host-patch characteristics and the conspecific female density in the patch. The offspring sex-ratio of single females presented with unparasitised hosts was female biased (approximately three daughters to one son in the progeny) whatever the host density tested. The sex-ratio in the presence of hosts parasitised by a conspecific 48 h beforehand was male biased. The proportion of male offspring also increased when the number of conspecific females exploiting the patch changed from a single female to a group of females, whatever the group size. No sexual differences in mortality as a result of larval competition on superparasitised hosts were observed. The offspring sex-ratios observed in response to the host-patch characteristics were the result of manipulation of the egg fertilisation by the females during the oviposition phase. Thus, the variability of the sex-ratio in response to an increase in the number of conspecific females in the same patch represented a reduction in egg fertilisation. These results are analysed with regard to the predictions of Local Mate Competition theory and the females' host discrimination ability.     

Response of the parasitoidEupelmus vuilleti to the odours of the phytophagous host and its host plant in an olfactometer

Eupelmus vuilleti (CRW) is a solitary ectoparasitoid which, under our experimental conditions, developed at the expense of the larvae and pupae ofBruchidius atrolineatus (Pic) (Coleoptera, Bruchidae). The larvae of this beetle are found inside the seeds of cowpea,Vigna unguiculata (Walp). Using a tubular olfactometer, we determined the olfactory stimuli involved in the orientation of females of the hymenopterous speciesE. vuilleti towards one of its hosts;B. atrolineatus. Several odours were tested including those from host plants ofB. atrolineatus, from non-host plants, from the host itself and from the waste products of the host. The odours of pods or dry seeds ofV. unguiculata (host plant of the phytophagous insect) affected the locomotor behaviour of females ofE. vuilleti. The odours from the plant in the vegetative stage had no effect. Kairomones from larvae, pupae or faeces ofB. atrolineatus were attractive to the parasitoid females. Odours from adult male or femaleB. atrolineatus, as well as the sex pheromone emitted by females were not attractive toE. vuilleti females. This sex pheromone did however stimulate the locomotor activity of the parasitoid. The adaptive significance of these olfactory stimuli is discussed.

---

Résumé Eupelmus vuilleti (CRW) est un ectoparasito?de solitaire qui se développe dans nos conditions expérimentales aux dépens des larves et des nymphes deBruchidius atrolineatus (Pic) (Coléoptère:Bruchidae). Les larves de ce Coléoptère se trouvent à l'intérieur des graines d'une LégumineuseVigna unguiculata (Walp). Grace à un olfactomètre tubulaire, nous avons déterminé les différents stimuli olfactifs intervenant dans l'orientation des femelles de cet hyménoptère, vers l;un de ses h?tes;Bruchidius atrolineatus. Plusieurs odeurs émanant soit de plantes-h?tes ou nonh?tes deB. atrolineatus, soit de l'h?te lui-même ou résultant de son métabolisme ont été testées. Les odeurs de gousses ou de graines sèches deVigna unguiculata Walp (plante-h?te du phytophage) influencent le comportement locomoteur des femelles. Par contre, les odeurs de plantes au stade végétatif n'ont pas d'effet. Les kairomones émanant de larves, nymphes ou fèces de larves deB. atrolineatus exercent un effect attractif sur les femelles parasito?des. Les odeurs émanant d'adultes males ou femelles deB. atrolineatus ainsi que la phéromone sexuelle émise par les femelles ne sont pas attractives pour les femelles deE. vuilleti. Cette phéromone sexuelle, par contre, stimule l'activité locomotrice des parasito?des. La signification adaptative de ces différents stimuli olfactifs est discutée.

     

Biology of Mastrus ridibundus (Gravenhorst), a potential biological control agent for area‐wide management of Cydia pomonella (Linneaus) (Lepidoptera: Tortricidae)

The codling moth Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) is a serious pest of pome fruit crops. A natural enemy of codling moth, the larval ectoparasitoid Mastrus ridibundus (Gravenhorst) (Hymenoptera: Ichneumonidae) has been imported into South America from the USA but little is known about the biology and ecology of the wasp, knowledge that is needed to design an efficient strategy of release and establishment. Experiments were carried out to assess important traits of the biology of the parasitoid in relation to its possible use as a biocontrol agent for codling moth. When M. ridibundus females were offered larvae ranging in weight from 37 to 78 mg, they oviposited more eggs on heavier hosts. In another study, the adult wasps were offered honey, diluted honey (10%) or pollen in paired choice tests and both males and females preferred honey over the other two foods. Females preferred 10% honey over pollen, while the males showed the opposite preference. Honey‐fed females lived longer than starved females. Adults died rapidly at 35°C, while they lived 20 days at 25°C and 12–17 days at 15°C. Female wasps had on average 25 ± 14 and 18 ± 11 progeny at 15 and 25°C, respectively, but they did not had progeny at 35°C. The development time (egg to adult emergence) was on average 44 ± 7 and 24 ± 2 days at 15 and 25°C respectively. Immature insects did not reach the adult stage at 35°C.     

Parasitism of Lacanobia oleracea (lepidoptera) by the ectoparasitic wasp, Eulophus pennicornis, disrupts the cytoskeleton of host haemocytes and suppresses encapsulation in vivo

Parasitism of Lacanobia oleracea larvae by the ectoparasitic wasp Eulophus pennicornis suppressed host haemocyte-mediated encapsulation of Sephadex DEAE A-25 beads in vivo. Beads dissected out of parasitized larvae had fewer haemocytes associated with them. Moreover, those haemocytes that were associated with the beads tended to retain a rounded configuration and rarely flattened. Similar results were obtained using in vitro encapsulation assays. SDS PAGE indicated that for parasitized and PBS injected larvae, there were some differences in the plasma proteins that bound to Sephadex DEAE A-25 beads, suggesting that parasitism-mediated changes to host plasma proteins might contribute to the differences in the encapsulation response occurring in these larvae. However, in vitro encapsulation assays using beads that had been pre-incubated in plasma from parasitized and unparasitized larvae, demonstrated that major differences in the extent of encapsulation did not occur. These results, plus in vitro haemocyte attachment and spreading assays, suggest that parasitism-mediated suppression of encapsulation is primarily due to reductions in the ability of host haemocytes to attach to (i.e., recognize) and flatten over non-self surfaces and other haemocytes. This proposal is corroborated by staining of actin in the haemocyte cytoskeleton by FITC-labelled phalloidin, which indicated that parasitism disrupts the formation of stress fibers and focal adhesions in plasmatocytes. By contrast, experimental injection of adult female wasp venom into unparasitized L. oleracea larvae had no significant effect on in vivo encapsulation responses or the haemocyte cytoskeleton. Arch. Insect Biochem. Physiol. 49:108-124, 2002. Published 2002 Wiley-Liss, Inc.