Article

Journal of Chemical Ecology

, Volume 20, Issue 11, pp 2901-2915

Interactions betweenAlloxysta brevis (Hymenoptera, Cynipoidea, Alloxystidae) and honeydew-collecting ants: How an aphid hyperparasitoid overcomes ant aggression by chemical defense

  • Wolfgang VölklAffiliated withLehrstuhl für Tierökologie I, UniversitÄt Bayreuth
  • , Gerhard HübnerAffiliated withLehrstuhl für Tierökologie I, UniversitÄt Bayreuth
  • , Konrad DettnerAffiliated withLehrstuhl für Tierökologie II, UniversitÄt Bayreuth

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Abstract

Foraging females of the aphid hyperparasitoidAlloxysta brevis were attacked by honeydew-collecting workers of the antLasius niger at the first encounter. However, ants abandoned their attacks quickly, and foragingA. brevis remained unmolested for a subsequent time interval of approximately 5 min, which is long enough for the hyperparasitoid to oviposit successfully. Furthermore, freshly killed intactA. brevis were disregarded by ants, while decapitated specimens were readily removed. We present evidence thatA. brevis females release a mandibular gland secretion, which contains 6-methyl-5-hepten-2-one, actinidin, and unidentified iridoids, in response to an ant attack. This secretion functions both as a measure of self-defense if the female is seized by an ant worker and as a repellent, which prevents ant attacks during subsequent encounters. This is the first evidence for chemical defense in a hymenopterous parasitoid. It enablesA. brevis females to hyperparasitize ant-attended aphids that constitute a major proportion of their hosts and significantly reduces mortality by ectohyperparasitoids.

Key words

Hymenoptera Alloxystidae hyperparasitoids ants Formicidae interactions aggression chemical defense 6-methyl-5-hepten-2-one actinidin biological significance