Natural History Photographs


Parasitic interactions: Parasitoids


Diptera, Acroceridae


Nederlands:Spinvliegen
English:hunch-back flies
Deutsch:Kugelfliegen
Spiders are among the most important predators of flies. Interestingly, there is one family of flies whose members 'return the favor', so to speak, namely the Acroceridae. Their larvae feed on spiders, rarely as ectoparasite but generally as endoparasite. In the end, the spider is doomed and dies, so these fly larvae are parasitoids. The adult flies have a very recognizable appearance, with a tiny head -whence they are called small-headed flies-, a humped thorax and a characteristic dumpy look altogether. Females lay enormous numbers of eggs that hatch into larva that actively search for a host. The large number of eggs indicates that success rate for the larva is very low.
Acrocera orbiculus
Authority:(Fabricius, 1787)
English:top-horned hunchback
Fochteloërveen, the Netherlands; 11 August 2012. Female.
Aekingerzand, the Netherlands; 1 August 2015.

Females. The vertical flight makes the humped body build less enigmatic.
Cyrtus gibbus
Authority:(Fabricius, 1794)
Synonyms:Syrphus gibbus Fabricius, 1794
Aizac (Ardèche), France; 3 August 2011.