56 
HALF HOURS WITH INSECTS. [Packard. 
while those unattacked had preserved their fresh color, and 
the tail moved about readily, the diseased ones becoming 
stiff and more or less dried. Mr: Putnam thinks that at 
least two-thirds of the chrysalides of this butterfly, hundreds 
of which had in the early autumn suspended themselves 
about his house and fences, had been attacked by these 
useful allies. 
On opening the body of the infested chrysalides I found 
about thirty parasites in different stages of growth, in one 
case thirty-two, in another only twelve. We can readily see 
Fig. 44. 
Parasite of Cabbage Butterfly 
how efficient these minute insects become in reducing the 
numbers of their hosts. A large proportion of the Ptero- 
mali undoubtedly winter over in the body of the chrysalis, 
the adult insects appearing in the spring. In England Mr. 
Curtis found the fly in June, so that evidently there is an 
autumn and spring brood of Chalcid flies. 
The male of this Pteromalus is a beautiful pale-green fly, 
with the body finely punctured and emitting metallic tints ; 
the abdomen, or hind body, is flat, in dried specimens with 
24 
