140 
Psyche 
[December 
maggots is agitated even slightly the parasites appear much 
disturbed and usually crawl out immediately. 
Once outside the dead host’s skin, the larva finds itself 
still a prisoner in the Cecropian cocoon. It never punctures 
this cocoon and not uncommonly dies from dehydration be- 
fore it can escape. The only way out is through the valve of 
the cocoon. The larva has no fear of dropping and its tough 
skin insulates it effectively from the shock of landing. In 
an experiment a handful of these larvae were tossed from a 
third-story window to cement below. Though bounding sev- 
eral feet with the force of the impact still they began to 
wriggle away immediately and in each case pupated later, 
apparently uninjured by the experience. 
Upon reaching the ground the maggot at once begins to 
push into the soil. The depth to which it penetrates depends 
on how far it must go to find reasonably damp soil, usually 
from three to eight inches. At the proper depth the soil is 
pushed out till a cell is formed in which the larva will either 
pupate after a few days and emerge as an adult in about a 
week or the larva will hibernate through the winter and 
pupate the following July. In the region studied the second 
brood of this tachinid in a summer was the exception rather 
than the rule. Proper moisture appears to be very necessary 
for the survival of the larva or puparium. For that reason 
puparia formed in the host cocoon where the larvse have 
failed to escape must immediately develop into adults or 
perish. If adults chanced to emerge in such situations, they 
could not escape from the host cocoon. In this study the 
only successful individuals were those which pupated in the 
ground. 
Three reasons why W. datanae is not a more effective 
parasite of Cecropia in the Chicago area are its habit of 
ovipositing only on mature larvae, the failure of many of the 
maggots to escape from the host cocoon, and the great 
sensitiveness to dehydration on the part of both hibernating 
larvse and the puparia. 
