The effects of group size and host species on development and survivorship of a gregarious caterpillar Halisidota caryae (Lepidoptera: Arctiidae)

Abstract. 1. The effect on growth and survivorship of the number of Halisidota caryae (Harris) caterpillars in groups feeding on three taxonomically distinct hosts was examined experimentally in the field. 2. Caterpillars grew more rapidly and survived better in larger sized groups than in smaller sized groups. 3. Caterpilliars grew more rapidly and survived better on Carya ovata (Koch) than on Hamamelis virginiana (L) or Quercus velutina (Lam.). 4. There were equal numbers of invertebrate predators on groups of different sizes and thus larger groups had significantly fewer predators per caterpillar than did smaller groups. 5. Invertebrate predators accounted for at least a 10% daily decrease in survivorship. 6. Local movement reduced predation because moving groups had fewer predators than did stationary groups.