Social biology of Liostenogaster vechti Turillazzi 1988 (Hymenoptera Stenogastrinae)

Liostenogaster vechti Turillazzi 1988, studied in Peninsular Malaysia, nests in huge aggregation of colonies, building its ring- or bracket-shaped nests on protected, smooth surfaces under overhanging rocks, bridge vaults etc. The biology and social behaviour of this species presents all the characteristics which set the Stenogastrinae aside from the other social vespids, i.e. production of an abdominal substance to help rear the immature brood, a three phase egg deposition, the presence of only four larval instars and the establishment of invariably small sized colonies. Colony life revolves round a dominant female, which has developed ovaries and spends most of her time on the nest. Colonies belonging to clusters from two separate localities showed a different percentages of potential egg layers per nest. In one cluster in particular, most of the colonies had only one egg layer, in spite of the differences in female population size. Like L. flavolineata (Cameron 1902), the colonial size of L. vecthi see..

The morphology of Van der Vecth's organ as a tool to measure caste dimorphism in Polistes paper wasps: a comparative approach

Given the centrality of chemical communication in social insects, there are many selective pressures acting on morpho-functional traits that mediate chemical pheromones. On the last gastral sternite of Polistes females, there is an important exocrine surface secreting chemical pheromone, named Van der Vecht's organ. It is involved in chemical defence of the nest, in rank and nestmate recognition, preventing workers from direct reproduction. Allometric differential growth of phenotypic traits between castes of social insects is generally considered as an indication of incipient physical castes. European Polistes present different nesting strategies and reproductive choices. Here, we carry out a comparison of Van der Vecht's organ size between castes of four European Polistes to provide a general measure of dimorphism. We show that Van der Vecht's organ of Polistes dominula and Polistes nimphus foundresses shows an allometric development being enlarged with respect to workers. Otherwise, no allometries have been highlighted in the other two studied species (i.e. Polistes associus and Polistes biglumis). Therefore, our data show that neither rigid monogyny nor specific nesting habits foster the evolution of true morphological castes in primitively eusocial taxa. Thus, at least two other species of Ezuropean Polistes show real evidence of incipient morphological castes

Reuse of old nests by the European paper wasp Polistes dominula (Hymenoptera Vespidae).

Similarly to the majority of social insects the nest represents for paper wasps an important component of the colony life and it is intimately linked to its social organization. When, in spring, future foundresses emerge from hibernacula they can choose between building a new nest and reusing an old one. Refurbishing the old nest in order to prepare it for a new breeding season cycle has already been observed in few species of paper wasps. In the present study we found that although the majority of Polistes dominula foundresses prefer to start new colonies early in the spring, an eight percent of nests were reused in our population. We speculate that reusing old nests might allow foundresses to save energy and gain time, but in turn it might also impose additional costs such as the risk of incurring in a higher pathogen pressure. Our data shows that the habits of reusing old nest is widespread in P. dominula but further experiments are required to test both these hypotheses and to clarify pros and cons of reusing old nests in this Polistes paper wasp species

Reuse of old nests by the European paper wasp Polistes dominula (Hymenoptera Vespidae).

Similarly to the majority of social insects the nest represents for paper wasps an important component of the colony life and it is intimately linked to its social organization. When, in spring, future foundresses emerge from hibernacula they can choose between building a new nest and reusing an old one. Refurbishing the old nest in order to prepare it for a new breeding season cycle has already been observed in few species of paper wasps. In the present study we found that although the majority of Polistes dominula foundresses prefer to start new colonies early in the spring, an eight percent of nests were reused in our population. We speculate that reusing old nests might allow foundresses to save energy and gain time, but in turn it might also impose additional costs such as the risk of incurring in a higher pathogen pressure. Our data shows that the habits of reusing old nest is widespread in P. dominula but further experiments are required to test both these hypotheses and to clarify pros and cons of reusing old nests in this Polistes paper wasp species

Can venom volatiles be a taxonomic tool for Polistes wasps (Hymenoptera, Vespidae)?

In the present study, we investigated whether venom volatiles have a species-specific composition and could possibly be used to discriminate between related paper wasp species. We compared venom volatile chemical profiles, obtained through gas chromatography-mass spectrometry analyses, of three non-parasitic European Polistes species (P. dominulus, P. gallicus and P. nimphus). The results show that the venom volatile composition is indeed species specific and can thus be a useful systematic tool