When wasps hitchhike on butterflies

Parasites abuse sex pheromones as a guidepost

Cabbage White © Duke University
Read out

Parasitic parasitic wasps use a sophisticated strategy to infest the eggs of their host animals. Using an anti-sex fragrance for butterflies, they locate their hosts and then ascend as blind passengers on mated female butterfly. They travel with them to their oviposition sites and then infest the freshly laid eggs.

Scientists at Freie Universität Berlin report this in a study now published in Nature. During mating, the butterfly larvae of the Great Cabbage White send a special fragrance called benzyl cyanide to their female partners, who repulses their male competitors as an anti-aphrodisiac.

The enemies of the cabbage white, tiny parasitic wasps, make use of this "chemical engagement ring": With the help of their antennae, the parasitic wasps perceive the perfume. In contrast to the butterfly male, they prefer to climb on the already paired and thus in an "anti-sex scent" wrapped female butterfly, while they have no interest in unpaired females.

The parasitic wasps fly with the paired and egg-ready female butterfly to the plants on which they lay the eggs. There, the wasps climb down from the unsuspecting "chauffeur" and stab into the butterfly eggs for parasitism. They kill off the descendants of their hosts.

However, when the virgin butterflies are treated with a synthetic anti-aphrodisiac, they suddenly become attractive to the parasites. Prof. Dr. med. Monika Hilker and Nina Fatouros from the Institute of Biology of the Free University Berlin together with colleagues from the Institute of Entomology of Wageningen University in the Netherlands. They have studied the unusual form of fragrance orientation of parasitic wasps. display

The caterpillars of the cabbage white are dreaded pests in agriculture. A use of these spy parasitic wasps could cause discarded cabbage white eggs to be killed before the caterpillars begin their feeding. Knowledge about the host-finding behavior of parasitic wasps can help to make biological pest control by parasitic wasps more effective and reduce the use of pesticides in the future.

(FU Berlin, 17.02.2005 - NPO)