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Chrysotoxum bicinctum

This attractive insect is one of the most distinctive hoverfly species in Ireland and can be readily  identified in the field by the combination of its yellow abdominal bars and the chocolate coloured  patches on the leading edges of its wings. The Chrysotoxum genus are unusual amongst Irish hoverflies in having long, slender antennae  projecting forward from the head (porrect), compared to the short and more or less rounded  antennae of most of the other species (compare with the antennae of Eristalinus aeneus). These  long antennae are similar to wasp antennae and Chrysotoxum species are imperfect wasp mimics.  Chrysotoxum bicinctum has been described as a mimic of the digger wasp Ectemnius continuus.  Although the resemblance (to a human eye) is not great, studies have shown that even slight  resemblance to noxious models can protect mimics from predators.  The larvae of Chrysotoxum species are believed to develop in ant nests where they  probably feed on root aphids, although little is known about the details of this association.  Chrysotoxum bicinctum is a widespread species in Ireland (distribution map), although it is  rarely encountered in large numbers. It is associated with a range of open semi-natural  habitats, as well as woodland clearings. In a survey of wetlands in Clare and south Galway, I  recorded it from 20 of the 31 sites studied, while I have also found it frequently in conifer  plantations, wet grasslands and peatlands. In conifer plantations it is associated with open  spaces along forest roads and in unplanted areas, and such features are important  for  maintaining hoverfly diversity, and biodiversity in general, within plantation forests. It is  largely absent from the improved grassland habitat that dominates most of the lowland  Irish landscape.   Because of its distinctive appearance, it is often recorded from casual observations (unlike  many other species, which require capture of specimens). However, I have not encountered it frequently in east Cork, with my only records coming from Ballyannan Wood and  Mitchell’s Wood near Castlemartyr. This may reflect the intensively farmed landscape with  little suitable unimproved grassland habitat. At Ballyannan Wood, I did not record  Chrysotoxum bicinctum in detailed surveys between 2003-2005, but it subsequently  appeared following the felling of stands of conifers, which created suitable areas of open  habitat. It does not appear to occur along the coastline in east Cork, despite apparently  suitable areas of unimproved grassland habitat.  Chrysotoxum bicinctum is a distinctive species that can be identified in the  field. Please submit any records to the National Biodiversity Data Centre 

Tom Gittings

Ecological Consultant