Laboratory feeding experiments on
Celerio euphorbiae(L.) showed that each larva consumed about 2.7 g dry weight of Euphorbia cyparissiasL. Laboratory-reared and field-collected larvae produced pupae of similar weights and the close similarity between the fresh and dry weights of control-fed larvae and larvae allowed to feed freely indicates that laboratory results are readily extrapolated to field conditions. On one infested site, at Braeside, Ont., the amount of spurge foliage was measured and the density of larvae needed to graze it fully was estimated at 14/m2 completing development. Preliminary data on an energy budget of the larva are discussed in relation to possible damage to the plant.