The venom apparatus in stenogastrine wasps: Subcellular features of the convoluted gland

In the wasp venom apparatus, the convoluted gland is the tract of the thin secretory unit, i.e. filament, contained in the muscular reservoir. Previous transmission electron microscope investigation on Stenogastrinae disclosed that the free filaments consist of distal and proximal tracts, from/to the venom reservoir, characterized by class 3 and 2 gland patterns, respectively. This study aims to extend the ultrastructural analysis to the convoluted tract, in order to provide a thorough, subcellular representation of the venom gland in these Asian wasps. Our findings showed that the convoluted gland is a continuation of the proximal tract, with secretory cells provided with a peculiar apical invagination, the extracellular cavity, collecting their products. This compartment holds a simple end-apparatus lined by large and ramified microvilli that contribute to the processing of the secretory product. A comparison between previous and present findings reveals a noticeable regionalization of the stenogastrine venom filaments and suggests that the secretory product acquires its ultimate composition in the convoluted tract.     

Suspending cocoons to evade ant predation in Meteorus pulchricornis, a braconid parasitoid of exposed-living lepidopteran larvae

We tested the hypothesis that cocoon suspension by a thread in hymenopteran parasitoids is a defense tactic against predators, by comparing predation against suspended and non-suspended cocoons of the braconid wasp Meteorus pulchricornis on a Quercus phillyraeoides hedge on which workers of the common small ant Crematogaster matsumurai were foraging. The lost proportion of non-suspended cocoons, which were artificially attached to leaves of Q. phillyraeoides , markedly decreased with cocoon age, indicating a critical phase of predation on young cocoons. No suspended cocoons at age 1–12 h at the beginning of exposure were lost within 12 h, whereas more than 75% of same-aged non-suspended cocoons were lost in the same period. Predation against such young cocoons would be a strong force driving the evolution of cocoon suspension in parasitoids of exposed-living host insects.     

杭州市螫人胡蜂种类及发生趋势分析

对杭州市消防部门2001~2004年为民摘除“马蜂窝”服务情况进行了调查,鉴定出螫人胡蜂有3种:墨胸胡蜂Vespa velutina nigrithoraxBuysson、拟大胡蜂Vespa analis nigransBuysson和亚非马蜂Polistesolivaceus(De Geer),其中墨胸胡蜂为主要危害种类,占所采集蜂巢的77.4%。从不同年份和月份、不同消防区摘除蜂巢服务资料统计结果看出,近年来胡蜂的发生数量呈上升趋势,每年6~10月份为高发期,城市中心区域是蜂巢的主要分布区,居民住宅是主要分布场所。并就治理方法进行了讨论。     

Comparative morphology of the skeletal parts of the sting apparatus of bees (Hymenoptera: Apoidea)

Details of the variation in sting morphology for all subfamilies of bees are presented for the first time. A considerable amount of variation, potentially of great utility for phylogenetic studies, has been discovered in every part of this complex structure. Additional probable synapomorphies of bees were found; these include loss of the specialized sensilla-bearing area at the apex of the gonostyli and the reduction and reorientation of the processi mediani at the base of the sting shaft. Synapomorphies for particular subtaxa of bees were found. These include a long, ventral emargination to the second valvifer in Nomiinae and a blister-like protrusion of the lamina spiracularis of the 7th hemitergite in the Megachilinae. Sting reduction and some details of sting morphology would seem to support a relationship between the Stenotritidae and Oxaeinae. Loss of sting function has occurred in four families of bees and repeatedly within the Andrenidae. In some instances loss of function as a sting is associated with increased development of certain structures indicating a change in function for the sting sclerites. It is suggested that all future studies of bee systematics above the species level should include assessment of variation of the sting apparatus and that sting preparations, made and stored in the same manner as preparations of male genitalia, become routine. © 2003 The Linnean Society of London, Zoological Journal of the Linnean Society , 2003, 138 , 1–38.     

Structure,biochemistry and ecology of entomogenous galls in Selaginella Pal. Beauv. (Selaginellaceae) from India

Abstract

We studied the structure of newly found entomogenous galls in three Indian species of Selaginella, and the biochemical changes during gall development as well as their seasonal abundances in 10 squares of 1.5 m² under two differing habitat conditions, open and covered. Adult wasps (Cynipidae) initiate two types of gall formation by oviposition, spherical galls on vegetative shoots and elongated, club-shaped strobilar galls on reproductive shoots. Galls are anatomically and biochemically different from the unaffected shoots. Vegetative shoot apices bear more galls (84.6%) than reproductive shoot apices (15.4%). Gall frequency is significantly higher in covered (94.8%) than in open habitat (5.2%), and its seasonal peak occurs earlier in the former (43.1% during the rainy season) than in latter habitat (52.8% in autumn). We discuss the relationship between relative species density and gall seasonality as well as the possible role of certain environmental factors that make covered habitats more favorable to the gall inducer.     

Effect of parasitoids,seed‐predators and ant‐mutualists on fruiting success and germination of Acacia drepanolobium in Kenya

Acacia drepanolobium is an obligate ant‐plant that bears dehiscent pods exploited by predispersal seed‐predators and parasitoids. Fruit set and seed germination in relation to ant‐association, bruchid and parasitoid infestation were investigated in a large‐scale multi‐year study in Kenya. Ant‐association had a significant impact on the overall numbers of fruiting trees. 94.8% of Crematogaster mimosae‐occupied trees, 25.6% of C. nigriceps‐occupied trees, and 82.2% of Tetraponera penzigi‐occupied trees set fruit. Within each tree, ant‐association had no significant impact on the amount of seed produced: C. mimosae‐occupied trees produced 47.5 seeds per branch, C. nigriceps‐occupied trees 44.9 seeds per branch and T. penzigi‐occupied trees 38.3 seeds per branch. Ant‐association did not limit seed‐predators or vary significantly by ant. Seeds infested by bruchids germinated in significantly lower proportions (6.2%) compared to uninfested seed (78.6%). Bruchid‐infested seed is also exploited by parasitoid wasps. Parasitoids appear to have a moderate but significant ‘rescue’ effect on bruchid‐infested seed with 18.4% of parasitoid‐infested seed germinating. Stable isotopes (δ15N) revealed the trophic structure of the seed‐associated insects, showing clearly that bruchids are seed predators and the parasitoid wasp Dinarmus magnus exploits the dominant Bruchidius sp.     

Variation in colour markings of German wasps Vespula germanica (F.) and common wasps Vespula vulgaris (L.) (Hymenoptera: Vespidae) in New Zealand

Abstract

German wasps (Vespula germanica F.) and common wasps (V. vulgaris L.) both show variations in colour markings in New Zealand. Overlap in the ranges of markings of the head and thorax is limited enough for ready distinction of queens and workers of the two species. Abdominal markings overlap considerably between the species. Colour markings of males were too similar to identify the species, which were completely separated by the shape of their genitalia. The frequency of occurrence of “intermediate” markings in V. germanica populations did not increase in areas where the two species overlap. This suggests there is little or no genetic exchange between the two species.     

First records of Synoeca septentrionalis Richards, 1978 (Hymenoptera, Vespidae, Epiponini) in the Brazilian Atlantic Rain Forest

Nests of Synoeca septentrionalis were collected in two Brazilian Atlantic Rain Forest localities (Itabuna and Santa Terezinha, in the state of Bahia and Alfredo Chaves in the state of Espírito Santo). Synoeca septentrionalis was previously recorded only from Central America and northwestern South America. This findingextends its geographical distribution to Northeast and Southeast regions of Brazil, and represents the first record for Synoeca septentrionalis in the Brazilian Atlantic Rain forest, raising to three the number of Synoeca species known from Bahia State.