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Scale Insects — Part 3

The insect is subject to the attacks of many natural enemies in the course of its growth. The little ladybirds, as the beetles of the family Coccinellidae are termed, both as larvae and adults feed upon these and other scales. There are five distinct species of chalcidid parasites which lay their eggs in the maturing bark-lice, and while the lice are young and before they have formed a protective scale they are avidly destroyed by the larvae of the syrphus flies, of the lace-winged flies, and by certain small predatory bugs. The most efficient of their natural enemies, however, are probably the ladybirds, since the writer has determined that the internal chalcidid parasites rarely destroy all of the eggs in the over-wintering scales. A large number of scales were examined in the late winter and early spring of 1894, with the result that when parasites were found from two to eighteen eggs were found to have escaped destruction, the average number of eggs in uninfested scales being from sixty-five to seventy-five. In two cases, where a parasite had issued late in the fall (and the small round hole of issuing is readily perceived in the scale), eleven and five eggs, respectively, were found. The ladybird, however, eats everything.