Limited overlap of the community of bees and wasps (Hymenoptera: Aculeata) nesting in reed galls with those nesting in other cavities

Hymenopterans occurring in wetlands represent specific community with bioindicative characters but poorly understood nesting biology. We have studied the nesting preferences of these insects in ten reed beds—five represented by natural wetlands, and the other five localized to anthropogenic sites. We reared the hymenopterans from trap-nests consisting of reed stalks and goldenrod stems, which were installed at the localities through the nesting season, and compared them with quantitative data of hymenopterans reared from reed galls collected at the same localities. Most of the species that nested in reed galls accepted the reed stalk traps but not vice versa. Some of the species that accepted both these nesting resources strongly differed in their frequency of use of these two nesting resources. Moreover, the species composition differed substantially between goldenrod stems and either reed stalks or reed galls. The digger wasp Pemphredon fabricii was eudominant in reed galls with higher abundance at anthropogenic sites, while it was also observed in reed stalks but in much lower numbers. Hylaeus pectoralis was frequent in reed galls at both habitat types and only one individual was reared from reed stalks. Trypoxylon deceptorium was quite numerous in reed galls but much more frequent in reed stalks. Species unknown from reed galls (Psenulus pallipes, Hylaeus confusus, Gymnomerus laevipes) were numerous in reed stalks. We experimentally confirmed that P. fabricii and H. pectoralis show high preference of reed galls and are dependent on these nesting resources. The available evidence suggests that the management of both natural and anthropogenic sites needs to implement tools preserving reed beds, especially the terrestrial ones with reed galls.     

Invaders on the move: parasitism in the sexual galls of four alien gall wasps in Britain (Hymenoptera: Cynipidae)

Four alien, host-alternating cynipid gall wasps are established in the British Isles: Andricus kollari, A. lignicola, A. quercuscalicis and A. corruptrix. Their current distributions divide Britain into four zones; all four invaders are present in the south and south-east of Britain, whereas only A. kollari is present in the far north of Scotland. The rank order, according to how far north the distributions of the four invading cynipid species reach, is: A. corruptrix→ A. quercuscalicis→ A. lignicola→ A. kollari. The life cycles of all four cynipid species involve a sexual generation in spring on Quercus cerris, and an agamic generation in autumn on Q. robur. Here we studied the parasitoid attack by four pteromalid species on the sexual generations of the invaders. We collected and reared the galls of all four species at eight sites from the south to the north of the country (two sites per zone). The geographical locations of the sites reflect the invasion history and thus the residence time of the alien species in the four zones. At each site we measured the densities of all host galls on Q. cerris and of both obligatory host-tree species. We also took a series of measures, such as host-tree density and mean host-tree size, to further characterize the tree stands. These measures are referred to as local parameters. Host densities varied between sites and between years. In A. kollari, galling rates were highest in the middle of the country (zone 2) in 1994, whereas in 1995 they increased from the south to the north. In A. lignicola, galling rates in both years were lowest at the sites in zone 3 (closest to its distribution boundary). In A. quercuscalicis, galling rates were found to be lowest at the site most to the north-west in both years, again the one furthest away from the area where this species was first recorded. Mortality caused by parasitoid attack differed from less than 10% to as high as 70% and varied between host species, sites and years. In four out of six cases the historical/regional variables (north/south and east/west) correlated significantly with parasitoid attack rates that were characteristically lowest at sites close to the distribution boundaries. Of the local factors, we found parasitoid attack rates correlated negatively in one case with host density, whereas they correlated positively in four cases with the density of alternative hosts of the parasitoids. In one of the models the local density of Q. cerris trees correlated negatively with parasitoid attack on A. quercuscalicis. For all three host species the terms retained in the minimal adequate models obtained for 1994 and 1995 differed, which might indicate that these communities of native parasitoids and invading host have not yet settled in any definite structure.     

Ant fauna associated with Microgramma squamulosa (Kaulf.) de la Sota (Polypodiaceae) fern galls

Galls are neoformed plant structures created by cell hyperplasia and hypertrophy induced by a number of organisms, especially insects. After adult insects hatch, senescent galls may remain on the host plant and be occupied by a succession of fauna, the most important and dominant being ants. This study aimed at characterizing the ant fauna successor of stem galls induced by microlepidoptera in Microgramma squamulosa (Kaulf.) de la Sota (Polypodiaceae). Four collections were carried out in the municipality of Nova Friburgo, Rio de Janeiro state, Brazil. The galls were packed in plastic bags and taken to the laboratory. Ants were euthanized and conserved in 70° GL alcohol and later identified. A total of 49 stem galls were collected and analyzed, 15 containing microlepidoptera galler larvae, one a parasitoid wasp and 33 without the microlepidoptera or parasitoid (67%). Twelve of these galls (39%) contained ants. Six ant species were recorded (Camponotus crassus, Crematogaster curvispinosa, Crematogaster sericea, Procryptocerus sampaioi, Tapinoma atriceps, and Wasmannia auropunctata), all native to Brazil. Ant occupation in M. squamulosa seems to be associated with senescent galls due to hatching of the galler insect, which leaves a hole that allows ants to colonize it, in other words, an opportunistic domatia. Senescent galls resulting from the death of galler insects do not seem to facilitate ant occupation.     

Industrial and post-industrial habitats serve as critical refugia for pioneer species of newly identified arthropod assemblages associated with reed galls

Gravel-sand river terraces were nearly eliminated from central European landscape by river channelization. Monotypic stands of common reed (Phragmites australis) growing on such terraces are often stressed by drought, which makes them vulnerable to Lipara spp. (Diptera: Chloropidae) gallmakers. Although Lipara are considered ecosystem engineers, only fragmentary information is available on the biology of their parasitoids and inquilines. We analyzed the assemblages of arthropods (Arachnida, Collembola, Dermaptera, Psocoptera, Thysanoptera, Hemiptera, Raphidioptera, Neuroptera, Coleoptera, Diptera, Lepidoptera and Hymenoptera) that emerged from 17,791 Lipara-induced galls collected in winter from 30 reed beds in the Czech Republic, 15 of which were situated at (post)industrial sites (gravel-sandpits, tailing ponds, limestone quarries, colliery dumps, and reclaimed lignite open-cast mines) and 15 were in near-natural habitats (medieval fishponds, and river and stream floodplains). The Chao-1 estimator indicated 229.3 ± 18.1 species in reed galls at (post)industrial and 218.1 ± 23.6 species at near-natural sites, with the Sørensen index reaching only 0.58. We identified 18 red-listed species and four new species for the Czech Republic (Gasteruption phragmiticola, Echthrodelphax fairchildii, Haplogonatopus oratorius and Enclisis sp.), representing mostly obligate (64 %) or facultative (9 %) reed specialists. We propose that Lipara gall-associated assemblages undergo a long-term cyclic ecological succession. During first 10 years after reed bed formation, only Lipara spp. and several other species occur. During next decades, the reed beds host species-rich assemblages with numerous pioneer species (Singa nitidula, Polemochartus melas) that critically depend on presence of prior disturbances. Middle-aged reed beds (near medieval fishponds) are prevalently enriched in common species only (Oulema duftschmidi, Dimorphopterus spinolae). Habitats with the longest historical continuity (river floodplains) host again species-rich assemblages with several rare species that probably require long-term habitat continuity (Homalura tarsata, Hylaeus moricei). Landscape dynamics is thus critical for the persistence of a full spectrum of reed gall inquilines, with (post)industrials serving as the only refugia for pioneer species ousted from their key nesting habitats at once cyclically disturbed gravel-sand river terraces.     

Hymenoptera aculeata of raised bogs in Belarus

The long-term studies (1986–2003) of raised bogs of Belarus revealed 167 species of aculeates belonging to 7 families: Sapygidae (1), Chrysididae (11), Pompilidae (19), Eumenidae (19), Vespidae (9), Sphecidae (76), and Apidae (32). The dominant species (not counting ants) are Vespula rufa (16.6%), Bombus jonellus (11.3%), B. lucorum (7.5%), Anoplius nigerrimus (5.1%), B. pascuorum (3.9%), Passaloecus turionum (3.8%), Argogorytes mystaceus (3.2%), Dipogon bifasciatus (3.1%), Pemphredon lugens (3.0%), and Trypoxylon attenuatum (2.6%). Approximately two-thirds of the species found in raised bogs nest in the upper layer. The spatial distribution of aculeates depends primarily on the distance from the bog margins and the presence of contrasting areas, such as lake banks or glades. The highest activity of various aculeate families (except for Vespidae) was observed in June. The total abundance of aculeates was found to be correlated with solar activity, the strongest correlation being observed in Vespidae. The abundance of different wasp families varied noticeably from year to year, depending on climatic parameters.     

New bethylid and chrysidid wasps (Hymenoptera: Chrysidoidea) from Canadian Late Cretaceous amber

A new bethylid species, Celonophamia granama, and two new chrysidid species, Procleptes eoliami, and P. hopejohnsonae, are described from Late Cretaceous (Campanian) amber collected at the Grassy Lake locality in Alberta, Canada. Within the deposit these taxa constitute the first bethylid, and the second and third chrysidid species to be described, respectively. The new taxa expand the sparse fossil record of Chrysidoidea, particularly that of Chrysididae—a group that was previously represented by only three described species in the Mesozoic. The presence of Celonophamia species in both Canadian amber and Siberian (Taimyr) amber further emphasizes faunal similarities between these two northern Late Cretaceous amber deposits. Given the prevalence of metallic coloration in Chrysididae, the specimens described here also provide evidence for the taphonomic alteration of perceived insect colors in Cretaceous amber inclusions.     

Biology of the solitary wasp Trypoxylon (Trypargilum) agamemnon Richards 1934 (Hymenoptera: Crabronidae) in trap‐nests

Buschini, M.L.T. and Fajardo, S. 2009. Biology of the solitary wasp Trypoxylon (Trypargilum) agamemnon Richards 1934 (Hymenoptera: Crabronidae) in trap‐nests. —Acta Zoologica (Stockholm) 91 : 426–432. Some Trypoxylon species build their nests in preexisting tubular cavities like hollow stems and beetle borings in branches. Study of the biology of these insects is relatively easy because the females of these wasps nest with enormous success in trap‐nests. The aim of this study was to investigate the abundance, seasonality and life‐history of Trypoxylon agamemnon. For capture of these insects, trap‐nests were installed in the Parque Municipal das Araucárias in araucaria forest, grassland and swamp, from December, 2001 to December, 2005. Two hundred and ninety seven nests were obtained. They were constructed more often during the summer (from December to April). The nests were built only in araucaria forest and consisted of a linear series of cells, divided by mud partitions, whose number varied from 1 to 7. Normally they have only one vestibular cell. The inner cells had been provisioned, usually with spiders of Anyphaenidae family. Sex‐ratio was strongly female biased. Its main natural enemies included Chrysididae, Ichneumonidae and Tachinidae.     

Nine new species of Dasineura (Diptera: Cecidomyiidae) from flowers of Australian Acacia (Mimosaceae)

Abstract. Thirteen species of Australian acacias are invasive plants in agricultural and native vegetation areas of South Africa. Biological control programmes for Australian acacias in South Africa have been implemented and are aimed at suppressing reproductive vigour and, in some cases, vegetative growth of these weeds. Gall-forming midges are under consideration as potential biological control agents for invasive acacias in South Africa. Entomological surveys in southern Australia found a diverse cecidomyiid fauna associated with the buds, flowers and fruits of Acacia species. Nine new Dasineura species are described and two species, D. acaciaelongifoliae (Skuse) and D. dielsi Rübsaamen, are redescribed. The newly described taxa are D. fistulosa sp.n. , D. furcata sp.n. , D. glauca sp.n. , D. glomerata sp.n. , D. oldfieldii sp.n. , D. oshanesii sp.n. , D. pilifera sp.n. , D. rubiformis sp.n. and D. sulcata sp.n. All eleven species induce galls on ovaries and prevent the formation of fruit. Two general types of gall are caused. Type A comprises woody, tubular galls with larvae living inside ovaries (D. acaciaelongifoliae, D. dielsi, D. fistulosa, D. furcata, D. glauca, D. glomerata, D. oldfieldii). Type B includes soft-tissued, globose galls that belong to four subtypes: inflated, baglike, hairy galls with larvae living between ovaries (D. pilifera); pyriform, pubescent swellings with larvae living inside ovaries (D. rubiformis); globose, hairy, swellings with larvae living superficially on ovaries in ovoid chambers (D. oshanesii); and inconspicuous, glabrous swellings with larvae living superficially on ovaries in shallow groovelike chambers (D. sulcata). The gall types are associated with a particular pupation pattern. In type A galls, larvae pupate within larval chambers in galls, whereas in type B galls pupation takes place between ovaries in galls or in the soil beneath the host tree. Gall midges responsible for the same general gall type are morphologically related and differ from species causing the other gall type. Phylogenetic analysis of a 410 bp fragment of the mitochondrial cytochrome b gene supports the division of the gall midge species into two groups except for D. sulcata, which appears as a subgroup of the group causing type A galls. The interspecific divergence values in group A species were between 0.5 and 3.9% with intraspecific divergence estimates of 0–0.2%. Gall midges causing type B galls had interspecific divergence values of 4.6–7.3% and intraspecific divergence values of 0–3.7%. Closely related biology and morphology together with low cytochrome b divergence estimates suggest a more recent speciation in group A when compared with species of group B. Dasineura rubiformis and D. dielsi are proposed as potential biological control agents for Acacia mearnsii De Wild. and Acacia cyclops A. Cunn. ex G. Don, respectively, in South Africa due to their narrow host range and ability to form high population densities that reduce seed formation. Both species produce galls with low biomass, which makes them compatible with commercial exploitation of their host species in Africa.     

闭弯尾姬蜂与菜蛾盘绒茧蜂寄生菜蛾幼虫时的种间竞争

在室内25℃下,以菜蛾3龄初幼虫作寄主,研究了菜蛾盘绒茧蜂Cotesia plutellae和半闭弯尾姬蜂Diadegma semiclausum的种间竞争。当寄主供2种蜂同时产卵寄生时,2种蜂各自的寄生率与其单独寄生时无显著差异,合计寄生率比一种蜂单独存在时有所提高,但差异不显著。2种蜂均能产卵寄生已被另一种蜂寄生了的寄主幼虫。当寄主被2种蜂寄生的间隔时间很短（少于10 h）时,所育出的蜂绝大部分（80%以上）为绒茧蜂;当寄主先被绒茧蜂寄生,并饲养2天以上再供弯尾姬蜂寄生时,所育出的全为绒茧蜂;当寄主先被弯尾姬蜂寄生,并饲养2天以上再供绒茧蜂寄生时,寄主幼虫绝大部分不能存活,只有少部分能育出寄生蜂,且多为弯尾姬蜂。当2种蜂的幼虫存在于同一寄主体内时,2种蜂的发育均受到另一种蜂的抑制;绒茧蜂1龄幼虫具有物理攻击能力,能将弯尾姬蜂卵或幼虫致死。这些结果表明,菜蛾盘绒茧蜂与半闭弯尾姬蜂在同一寄主中发育时,前者具有明显的竞争优势。     

Impact of αAI-1 Expressed in Genetically Modified Cowpea on Zabrotes subfasciatus (Coleoptera: Chrysomelidae) and Its Parasitoid,Dinarmus basalis (Hymenoptera: Pteromalidae)

Genetically modified (GM) cowpea seeds expressing αAI-1, an α-amylase inhibitor from the common bean, have been shown to be immune against several bruchid species. Effective control of such pests by growing GM cowpea could promote the spread of bruchid species that are αAI-1 tolerant. Consequently, the sustainability of bruchid pest control could be increased by combining GM seeds and hymenopteran parasitoids. However, there are concerns that αAI-1 could interfere with the biological control provided by parasitoids. Here, we assessed the impact of GM cowpea seeds expressing αAI-1 on the αAI-1-tolerant bruchid Zabrotes subfasciatus and its parasitoid Dinarmus basalis. αAI-1 in cowpea seeds did not increase resistance to Z. subfasciatus or affect the mortality rate of Z. subfasciatus larvae. Parasitism of Z. subfasciatus by D. basalis and fitness of D. basalis offspring were not affected by the presence of αAI-1. Thus, αAI-1-expressing cowpeas and parasitoids should be compatible for the control of bruchid pests.     

An endoparasitic species of Pteromalidae (Hymenoptera: Chalcidoidea) attacking Aphidoletes aphidimyza (Diptera: Cecidomyiidae)

A solitary endoparasitic species of Pteromalidae (Hymenoptera: Chalcidoidea) was reared from pupae of an aphidophagous gall midge, Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae), in Japan. The parasitoid was identified as Gastrancistrus fuscicornis Walker, a species that has been recorded from Europe. An unidentified aphid has been proposed as being a host of G. fuscicornis, but the study reported here confirmed that G. fuscicornis is an endoparasitoid of A. aphidimyza. I consider that G. fuscicornis may not be a parasitoid of aphid. I found a nontentorial pit on the head of male and female of G. fuscicornis. According to the definition of the nontentorial pits, the pit found in G. fuscicornis corresponds to the facial pit. This is the first finding of the facial pit in Chalcidoidea. Morphological differences between G. fuscicornis and its allied species are provided.     

Nesting biology of three Megachile (Hymenoptera: Megachilidae) species from Eastern Amazonia,Brazil

Megachile Latreille is a conspicuous genus of solitary bees distributed worldwide. However, the biology of tropical species is still little known. We present data on biology of Megachile brasiliensis Data Torre, Megachile sejuncta Cockerell and Megachile stilbonotaspis Moure found in two remnants of eastern Amazonian forest in northeastern Brazil. The study was conducted using the trap-nest methodology in two different areas during four periods. We collected a total of 24 nests of M. brasiliensis, 26 of M. sejuncta and 28 of M. stilbonotaspis. The differential abundance of collected nests may reflect the population size in each sampled place. The nesting activity was concentrated mainly between July and January and species presented a multivoltine pattern, except for M. sejuncta, which was partly univoltine. Assessed pollen use showed a predominant use of Attalea sp. (Arecaceae) and, for M. stilbonotaspis, Tylesia sp. and Lepidaploa sp. (Asteraceae). Babassu is a very common palm in the studied areas and the studied species seem to have a strong link with it. We also reported change of pollen use by M. sejuncta, probably due to competition with M. brasiliensis, which may have influenced the biased sex ratio observed in M. sejuncta toward males. Parasites reported here were also recorded for other Megachile species, such as Coelioxys, Brachymeria, Meloidae and Pyralidae species. Mites were observed in association with M. stilbonotaspis. The data presented here set up a background that encourages new studies on the ecology of these three Amazonian species, providing tools for proper biodiversity management and conservation.     

Non-target host risk assessment of the idiobiont parasitoid Bracon celer (Hymenoptera: Braconidae) for biological control of olive fruit fly in California

Non-target risk posed by an African parasitoid, Bracon celer Szépligeti (Hymenoptera: Braconidae), was assessed for a classical biological control program against olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae: Dacinae), in California, USA. Behavioral and reproductive responses to non-target tephritid species were tested with beneficial (Chaetorellia succinea [Costa] and Parafreutreta regalis Munro) (Tephritidae: Tephritinae) and native (Rhagoletis fausta [Osten Sacken]) (Tephritidae: Trypetinae) fruit fly species in successive no-choice and choice experiments under close confinement in quarantine. Non-target host-plant substrates exposed to B. celer were yellow-starthistle flower heads containing C. succinea, Cape ivy stem galls containing P. regalis, and bitter-cherry fruit containing R. fausta. The parasitoid probed all three infested non-target plant substrates, but significantly less than olives infested with B. oleae. It produced offspring from P. regalis in Cape ivy stem galls, but appeared unable to penetrate yellow-starthistle flower heads with its ovipositor. Bracon celer killed some B. oleae and R. fausta larvae without parasitism. Reproduction on P. regalis indicates that B. celer has a broad physiological host range, which, combined with the parasitoid's acceptance of all three host-plant substrates, indicates a strong potential to negatively impact non-target species. Although physical and temporal barriers to host attack may reduce risk to most non-target tephritids by B. celer in California, the parasitoid should not be released due to its risk of harming the beneficial P. regalis. Release of P. regalis is still under consideration, however, and final risk assessment should depend on whether the fly proves useful for weed control.     

Distribution of 18S rDNA sites and absence of the canonical TTAGG insect telomeric repeat in parasitoid Hymenoptera

Karyotypes of six species belonging to three main clades of parasitoid Hymenoptera, the superfamilies Ichneumonoidea (Ichneumonidae: Ichneumon amphibolus), Cynipoidea (Cynipidae: Diplolepis rosae) and Chalcidoidea (Eurytomidae: Eurytoma robusta, Eu. serratulae and Eu. compressa, and Torymidae: Torymus bedeguaris) were studied using FISH with 18S rDNA and telomeric (TTAGG)_n probes. Haploid karyotypes of D. rosae, Eu. robusta and Eu. serratulae carried the only 18S rDNA hybridization signal, whereas those of I. amphibolus and Eu. compressa carried three and two rDNA clusters respectively. In addition, three rDNA sites were visualized in the aneuploid female of T. bedeguaris. The number of rDNA clusters in parasitoid Hymenoptera generally correlates to the chromosome number. Apart from the overwhelming majority of the studied species of aculeate Hymenoptera, no hybridization signals were obtained from FISH with the telomeric (TTAGG)_n probe in the examined parasitoid species. These data suggest absence of the canonical (TTAGG)_n insect telomeric motif in the Ichneumonoidea, Cynipoidea and Chalcidoidea, and perhaps in parasitoid Hymenoptera in general.     

The Significance of the Vestibular Cell in Trap Nesting Wasps (Hymenoptera: Crabronidae): Does its Presence Reduce Mortality?

In a study carried out with the trap-nesting solitary wasp Trypoxylon attenuatum (Hymenoptera: Crabronidae) in 2000, we analysed the significance of different nest characteristics, like the vestibular cell and empty intercalary cells, and its role in the reduction of mortality. Analysis of the presence of the vestibular cell suggested that it represents a nest completion structure, whose presence reduces mortality in the initial stages (M1) but does not affect that due to chrysidid parasitoids (MP). The length of such vestibular cell was found to depend mainly on the space between the last provisioned cell and the exterior, pointing to a possible role in the reduction of the remaining space that could be used by other females to establish a nest exterior to the completed one. The empty intercalary cells were smaller than the vestibular cells, did not affect M1 or MP mortality rates in the nest, and exhibited an “aggregated” pattern of occurrence. This suggests that they could be the result of “abnormal” behaviour by the female owning the nest. The total mortality rate decreased with the increase in the number of cells in the nests, also being greater in nests established at low heights above the ground. M1 was lower in the innermost cells, while MP increased towards the interior and in the nests with more cells. The distribution in the nests of cells parasitized by Trichrysis cyanea (the main natural enemy found in the wasp population studied) reflects an “aggregated” pattern, suggesting repeated attacks against certain nests.     

Interactions between Spathius agrili (Hymenoptera: Braconidae) and Tetrastichus planipennisi (Hymenoptera: Eulophidae), larval parasitoids of Agrilus planipennis (Coleoptera: Buprestidae)

Three hymenopteran parasitoids native to China are being released in the United States as biological control agents for the emerald ash borer (EAB), Agrilus planipennis Fairmaire, an Asian buprestid species responsible for mortality of ash trees (Fraxinus spp.) in North America. Two of these hymenopterans, Spathius agrili Yang (Braconidae), a larval ectoparasitoid, and Tetrastichus planipennisi Yang (Eulophidae), a larval endoparasitoid, prefer late-instar EAB larvae. This overlapping host preference raises concerns that interspecific competition following field releases may compromise establishment of one or both species. In a series of laboratory and field experiments, we found S. agrili and T. planipennisi exhibited similar parasitism rates when presented alone with EAB larvae for 12–14 days. However, S. agrili was more efficient at locating and parasitizing hosts within the first 27 h, possibly explaining why S. agrili excluded T. planipennisi in the laboratory trials and nearly excluded T. planipennisi in field trials when the two species were presented together with EAB larvae. We found that S. agrili parasitized larvae previously parasitized by T. planipennisi but not the reverse. However, S. agrili offspring failed to complete development on hosts that were previously parasitized by T. planipennisi. We recommend releasing these species separately in time or space to avoid the antagonistic interactions observed in this study.     

Parasite presence acts as a proximate cue in the nest-site selection process of the solitary digger wasp,Ammophila dysmica (Hymenoptera: Sphecidae)

Nest-site selection by the solitary ground-nesting wasp Ammophila dysmicaMenke was studied during 1982–1986 in California's Sierra Nevada Mountains. Digging females detected and discriminated among members of a complex of insect intruders, including a number of predators and parasites. In response to some natural enemies, wasps sometimes permanently abandoned nests under construction. These selective nest abandonments reduced the mean number of cleptoparasitic chrysidid wasps, Argochrysis armillaBohart, attending the excavation of completed nests. The number of A. armillaattending a nest excavation correlated positively with the probability of nest parasitism by this species. Selective nest abandonment may reduce parasitism rates.     

Effect of ellagic acid on the larvae of Spodoptera litura (Lepidoptera:Noctuidae) and its parasitoid Bracon hebetor (Hymenoptera:Braconidae)

The present study was aimed at investigating the effect of plant based compound, ellagic acid on parasitoid Bracon hebetor (Say) through its host, the common cutworm, Spodoptera litura (Fabricius). The effect on S. litura was ascertained by feeding six days old larvae on artificial diet incorporated with different concentrations (5 ppm, 25 ppm, 125 ppm, 625 ppm, 3125 ppm) of ellagic acid and water as control. Its effect on B. hebetor was determined by allowing the adult B. hebetor to parasitize the treated host larvae. The mortality of S. litura larvae was increased whereas adult emergence declined with increasing concentration of ellagic acid. The developmental period was delayed significantly and all the nutritional indices were reduced with treatment. Ellagic acid at LC₃₀ (7.70 ppm) had not much influence on the growth of parasitoid B. hebetor but LC₅₀ (43.45 ppm) adversely influenced the development of the parasitoid, B. hebetor when reared on treated larvae of S. litura. This was evident from reduced parasitization, fecundity, egg laying, egg hatching, emergence, increased larval mortality, reduced pupation and prolonged development of the immature stages at LC₅₀. However, parasitization, egg hatching and larval mortality of the parasitoid were not significantly impacted at LC₃₀ indicating the possibility of its use in integrated pest management programmes.     

Population responses of hymenopteran parasitoids to the emerald ash borer (Coleoptera: Buprestidae) in recently invaded areas in north central United States

Populations of hymenopteran parasitoids associated with larval stages of the invasive emerald ash borer (EAB) Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) were surveyed in 2009 and 2010 in the recently invaded areas in north central United States (Michigan), where two introduced EAB larval parasitoids, Tetrastichus planipennisi Yang and Spathius agrili Yang were released for classical biological control. Results from two years of field surveys showed that several hymenopteran parasitoids have become associated with EAB in Michigan. Among these parasitoids, the gregarious species T. planipennisi was the most abundant, accounting for 93% of all parasitoid individuals collected in 2009 (immediately after field release) and 58% in 2010 (a year later after field releases). Low levels (1–5%) of parasitism of EAB larvae by T. planipennisi were consistently detected at survey sites in both years. Separately, the abundance of the native parasitoid, Atanycolus spp., increased sharply, resulting in an average parasitism rate of EAB larvae from <0.5% in 2009 to 19% in 2010. Other parasitoids such as Phasgonophora sulcata Westwood, Spathius spp., Balcha indica Mani & Kaul, Eupelmus sp., and Eurytomus sp. were much less abundant than T. planipennisi and Atanycolus spp., and each caused <1% parasitism. Besides hymenopteran parasitoids, woodpeckers consumed 32–42% of the immature EAB stages present at our study sites, while undetermined biotic factors (such as microbial disease and host tree resistance) caused 10–22% mortality of observed EAB larvae. Relevance of these findings to the potential for biological control of EAB in the invaded areas of North America is discussed.     

Host Plants Affect the Foraging Success of Two Parasitoids that Attack Light Brown Apple Moth Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae)

The light brown apple moth, Epiphyas postvittana is a key pest of wine grapes in Australia. Two parasitoids, Dolichogenidea tasmanica and Therophilus unimaculatus, attack the larval stage of this pest. D. tasmanica is dominant in vineyards, whereas T. unimaculatus is mainly active in native vegetation. We sought to understand why they differ in their use of habitats. Plants are a major component of habitats of parasitoids, and herbivore-infested plants influence parasitoid foraging efficiency by their architecture and emission of volatile chemicals. We investigated how different plant species infested by E. postvittana could affect the foraging success of the two parasitoid species in both laboratory and field experiments. Four common host-plant species were selected for this study. In paired-choice experiments to determine the innate foraging preferences for plants, both parasitoid species showed differences in innate search preferences among plant species. The plant preference of D. tasmanica was altered by oviposition experience with hosts that were feeding on other plant species. In a behavioral assay, the two parasitoid species allocated their times engaged in various types of behavior differently when foraging on different plant species. For both parasitoids, parasitism on Hardenbergia violacea was the highest of the four plant species. Significantly more larvae dropped from Myoporum insulare when attacked than from the other three host-plant species, which indicates that parasitism is also affected by interactions between plants and host insects. In vineyards, parasitism by D. tasmanica was significantly lower on M. insulare than on the other three host-plant species, but the parasitism rates were similar among the other three plant species. Our results indicate that plants play a role in the habitat preferences of these two parasitoid species by influencing their foraging behavior, and are likely to contribute to their distributions among habitats.