When is a Wasp a Fly?

Conops quadrifasciatus

With its narrow waist and yellow and black striped colouration, one would be forgiven for assuming Conops quadrifasciatus was a solitary wasp. Closer inspection however reveals one set of wings, as opposed to hymnopterans' two sets, which places it firmly with the dipterans. C. quadrifasciatus is one of a number of similar conopid flies that are present in Europe (1), with 11 species of the family present in Ireland (2). Adults feed on a variety of flowers, including ragwort (Senicio jacobaea) as seen in the pictures.

Conops quadrifasciatus

However, any affinity conopid flies have with hymnopterans is entirely superficial as they are major parasites of bumblebees. The adult female fly attacks foraging worker, male and queen bumblebees outside the nest, placing eggs onto or in the abdomen of the host. The larva hatches and resides in the abdomen of the bee, feeding off haemolymph and the bee's internal organs (3). The bee dies during the last larval stage and pupation takes place inside the body of the bee.

References:

1. Chinery, 1997. Collins Gem Insects p. 202
2. Ferriss et al. 2009, Irish Biodiversity: A Taxonomic Inventory of Fauna p.101
3. Schmid-Hempel et al., 1990. Insectes Sociaux 37 pp. 14-30