Aprosthema larva multiparasitized by Lathrolestes and Ischyrocnemis, with Lathrolestes surviving

An Aprosthema tardum (Klug, 1814) (Hymenoptera: Tenthredinoidea, Argidae) larva is multiparasitized by Ischyrocnemis goesi (Holmgren, 1558) (Hymenoptera: Ichneumonidae, Ctenopelmatinae) and Lathrolestes erythrocephalus (Gravenhorst, 1829) (Hymenoptera: Ichneumonidae, Ctenopelmatinae)

A third instar, 7 mm, Aprosthema tardum larva is found feeding on its host plant Lathyrus latifolius.
It has three white bean-shaped endoparasitoid eggs in its body and is thus superparasitized by Ischyrocnemis goesi.

Most probably the host larva has been parasitized some days before by Lathrolestes erythrocephalus, because the next day, a first instar Lathrolestes erythrocephalus larva moves inside the host, and it seems that the eggs of Ischyrocnemis goesi have not yet hatched. Normally first instar Lathrolestes erythrocephalus larvae hatch after about 5 days, and Ischyrocnemis goesi eggs are not visible any more after about three days.

In its first instar, the Lathrolestes erythrocephalus larva is adapted for fighting competitors, with its big head and mandibles, and actively searches for them inside the host. Generally, when there are more endoparasitoids eggs, the larva from the first egg to hatch will win because it can kill the other eggs easily. If they are more first instar larvae at the same time, though, they have to fight!

When it has reached maturity, the host larva spins a winter cocoon, from which a Lathrolestes erythrocephalus emerges the following spring.


Shaw, M.R., Kan, P., Kan-van Limburg Stirum, B. & Wahl, DB. (2022) - Biological and morphological studies on the parasitoids (Hymenoptera, Ichneumonidae) of Aprosthema tardum (Klug) (Hymenoptera, Argidae, Sterictiphorinae) in Var, southern France. Journal of Hymenoptera Research.
https://jhr.pensoft.net/article/82107/