Paper Wasp Shaves (?) Caterpillar – Ron Goor (2013)

The behavior of this paper wasp worker was recorded by Ron Goor in C & O Canal in Seneca Maryland, United States. At first glance it looks quite curious since it appears as if the wasp is shearing its prey like a sheep. However when viewed carefully the wasp is simply consuming the caterpillar most probably belonging to Virginian Tiger Moth (Spilosoma virginica) before flying back to its nest. While the worker wasp is literally taking “her cut” from the prey some of the unconsumed fuzzy hairs fall off on the leaf she is standing. The half-consumed caterpillar serves as food for the wasp larvae. A similar behavior was observed in a different wasp species (Polistes carolina) attacking in red striped grasshopper (Romalea microptera) where prey was partially consumed before returning to nest.

Nevertheless, the behavior is a good material for discussion of the parent-offspring conflict in evolutionary biology. A caretaker must adjust her behavior optimally so that she herself doesn’t suffer in the long run by over-investing in the offspring.

There is also another side to the behavior articulated here. Although the caterpillar is paralyzed and completely incapacitated, its protective hairs still may bear highly potent poisonous chemicals. These chemicals are metabolically quite costly to produce. For this reason even the caterpillars who shed their own skin from one growth stage to the other consume their own discarded skin. Perhaps the wasp herself benefits from the defensive chemicals by reducing palatability. In marine habitats aeolid nudibranchs are known for their “cleptocnidae” – stinging capsules containing chemicals that are accumulated from the cnidarians eaten by the nudibranchs.

From the caterpillar side, these chemicals are purely defensive to deter parasitoids who attack caterpillars to lay their eggs inside them. Parasitoids are parasites who ultimately kill their hosts before they emerge. Parasitoid ichneumon wasps are one of the most interesting examples of parasitoid evolution possessing the longest ovipositor in animal kingdom.