Insect Identification sample sheet
Aphid hyperparasites - Alloxysta & Phaenoglyphis
These two genera of cynipoid wasps (Hymenoptera, Cynipoidea) are hyperparasites of aphids via other small parasitic wasps (Hymenoptera - Braconidae or Chalcidoidea). The adult female Alloxysta approaches and palpates aphids until it locates one that is parasitized by the larva of a braconid or chalcid wasp; it then orientates itself head to head and inserts its ovipositor into the aphid's abdomen, and an egg is inserted into the body cavity of the primary parasite larva which lies in the body cavity of the aphid.
Sometimes unparasitized aphids are probed but no egg is laid. Alloxysta develops within the body cavity of the host wasp until the host has grown, killed the aphid and spun its cocoon - only then does the hyperparasite kill the primary parasite. At this stage the aphid is only a ìmummifiedî shell. The Alloxysta larva does not spin a cocoon but pupates within the aphid on what remains of its primary host. The adult Alloxysta then chews a hole through the abdomen of the aphid and emerges ready to mate and start the cycle again.
These wasps are difficult to identify; they are all small (2 mm or less in length), with a very smooth and shiny thorax and all have the distinctive triangular cell in the forewing which is one of the characteristic features of the Cynipoidea. The British species are revised in:
Fergusson, N.D.M. 1986. Charipidae, Ibaliidae & Figitidae (Hymenoptera: Cynipoidea). Handbooks for the Identification of British Insects, 8 (1c) 1-55pp.
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