Feeding scents guide hyperparasitoid wasps to their aphid hosts

The hyperparasitoid wasp Alloxysta fuscicornis deposits her eggs – via her ovipositor – into a primary parasitoid larva inside the body of the cabbage aphid Brevicoryne brassicae, during a rodeo-style ride on the aphid. Foto: Hans Smid, bugsinspace.nl

 

Changes in the feeding behaviour of infected aphids lead hyperparasitoid wasps to their targets via plant volatiles.

 

A further level of chemical espionage between parasitoid wasps and aphids has been mapped by entomologists at Wageningen. The hyperparasitoid wasp Alloxysta fuscicornis can distinguish the odour signature of already-parasitised cabbage aphids (Brevicoryne brassicae) from that of healthy aphids, enabling it to successfully deposit eggs – using its ovipositor – into primary parasitoid larvae concealed within aphid bodies (New Phytologist, 15 December, online).

 
Choice experiments
To do this, the hyperparasitoid wasp leaps onto a parasitised cabbage aphid. ‘It looks a bit like a rodeo ride’, says lead author Michel Bourne, now a postdoc at the University of Zurich, in an accompanying video. Choice experiments in Y-tubes experimentally demonstrate that A. fuscicornis can smell the difference between the feeding volatiles of parasitised and unparasitised aphids. The electrical signals from ‘tethered’ aphids were then recorded via gold wires, revealing that parasitised aphids drink more xylem sap, whilst healthy aphids predominantly feed on sugar-rich phloem sap.

 
Principal investigator and senior author Erik Poelman finds it remarkable that a similarly functioning multitrophic interaction – previously discovered by their group in hyperparasitoid wasps on caterpillars (PLOS Biology, 2012) – has now also been demonstrated for aphids. ‘Whereas aphids feed on the plant in a completely different way from caterpillars, and the physiological response of the plant also differs.’
 
See also:
–The problem of a hyperparasitic wasp – Video Bugs in Space, 8 October 2025