Parasitoids of the Wild Silk Moths (Saturniidae)

by Kirby L. Wolfe

Eupelmid Egg Wasp

Parasitoid: What is a parasitoid? The letters “oid” mean “like” and so it’s an organism like a parasite. It’s actually somewhere between a parasite and a predator. It kills its host like a predator, but it lives in its host first, like a parasite. Most parasitoids are small wasps, but some kinds of flies and even slender hairworms can be parasitoids of saturniid moths.

Eupelmid Egg Wasp (Anastatus sp.). Members of the family of small wasps called Eupelmidae are often hyperparasitoids or egg parasitoids. Hyperparasitoid larvae may live inside parasitoid larva which may live inside moth larvae. One genus of eupelmid wasp is Anastatus, whose many tiny species are all parasitoids of insect eggs.

The wasp pictured here is a species of Anastatus that emerged from an egg of the Walters Silk Moth (Saturnia walterorum). The adult is like a tiny ant, about 3/32 inch (2 mm) long.

Most wild silk moths place their eggs in groups, and, if a female wasp finds them, she walks around on the eggs pushing her ovipositor (stinger) through each eggshell to place a wasp egg inside. If the female wasp has mated with a male, her eggs will develop into males and females, but if she has not found a mate before ovipositing (laying), all the wasps that develop from her eggs will be males. Sometimes more than 90% of a moth’s group of eggs will contain wasp larvae.

Reference: Richard S. Peigler. Catalog of Parasitoids of Saturniidae of the World. Journal of Research on the Lepidoptera 33:1-121, 1994.

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