Density-dependent processes in leaf beetles feeding on purple loosestrife: aggregative behaviour affecting individual growth rates

Aggregative responses are commonly observed in insects, including chrysomelids, affecting both individual and population growth rates. In two closely related chrysomelid beetles (Galerucella calmariensisandG. pusilla) feeding on purple loosestrife (Lythrum salicaria), recent studies suggest that male-produced pheromones may cause both inter- and intraspecific attraction. This paper further examines the causes and consequences of feeding aggregations in these species. Olfactometer studies confirm previous findings, showing cross-species attraction to damaged plants, but suggest that also damaged induced plant volatiles may be involved. In addition, the studies suggest that the cross-species attraction observed in previous studies have asymmetric effects on the two beetles.Galerucella pusillawas more attracted to damage byG. calmariensisthan to damage by conspecifics. Laboratory and field data suggest that feeding aggregations in these species increase pupal mass, at least at low to intermediate larval densities. This positive feedback may have important consequences for the spatiotemporal dynamics and as a consequence on the role of the two chrysomelid beetles on biological control of purple loosestrife.

A new species of Hoplosaenidea Laboissiere, 1933 from Malaysia (Coleoptera: Chrysomelidae: Galerucinae)

Recently, the author described two species of the genus Hoplosaenidea Laboissiere, 1933 (Coleoptera: Chrysomelidae: Galerucinae) where the male having a peculiar secondary sexual characters: clypeus excavated, furnished with projections, and the antennal first segment large, broadened, excavated and spined at apex. The two species are H. takizawai Mohamedsaid, 2001 (Fig. 5) and H. singaporensis Mohamedsaid, 2002 (Fig. 6) described from Bali and Singapore, respectively. The presence of secondary sexual characters in males is most prevalent in the chrysomelid beetles of the subfamily Galerucinae (Mohamedsaid 2004b).

Systematics and phylogeny of Chrysomelobia species (Acari:Podapolipidae), sexually transmitted parasites of chrysomelid beetles

Chrysomelobia Regenfuss and Parobia Seeman & Nahrung are sexually transmitted mites, the former being parasites of chrysomelid beetles in the Americas, Europe and Africa, the latter a radiation on the Paropsini (Chrysomelidae) in Australia. A cladistic analysis of Chrysomelobia and Parobia shows the type species of Chrysomelobia, C. mahunkai Regenfuss, is placed within Parobia. Therefore, Parobia is synonymised with Chrysomelobia, which has priority. I describe another nine new species of Chrysomelobia from Australian paropsine beetles: C. aquariolus, sp. nov., C. orthagoriscus, sp. nov. and C. cubile, sp. nov. from Paropsis porosa Erichson; C. lipsettae, sp. nov. from Dicranosterna pedestris (Chapuis); C. armstrongi, sp. nov. from Paropsisterna sp. nr minerva (Blackburn); C. pagurus, sp. nov. from Paropsis charybdis Stål; and C. nahrungae, sp. nov., C. vafer, sp. nov. and C. verecundus, sp. nov. from three species of Trachymela. Chrysomelobia captivus (Seeman & Nahrung) is recorded from Paropsisterna nobilitata (Erichson) for the first time. Most Australian members of Chrysomelobia are host-specific and beetles may host up to three mite species. Within species-groups of mites, species that share the same host genus are closely related. However, mite species that share the same host species are usually from different species-groups of mites. Although these patterns suggest co-speciation at terminal nodes and host transfers at deeper nodes, little can be made of these patterns without a host phylogeny. Keys to Chrysomelobia adults are provided.