14 
Psyche 
[February 
About Amherst, Massachusetts, Trichopoda pennipes ap- 
pears to have two full generations each year (Worthley, 1923). 
A single adult captured in October may indicate a partial third 
generation, but it is thought more probable that this was a 
laggard individual of the second generation. 
The emergence and pupation of second generation larvae 
in the fall was not observed in the cages, and it therefore appears 
that the parasite passes the winter as a larva within the body of 
the hibernating host. Development of these larvae is completed 
in the spring, emergence from the host and pupation occurring 
during June and July. This emergence is shortly followed by 
the death of the host, which, in all cases so far observed, has not 
been able to commence egg-laying. 
Pupae developing from these overwintered larvae begin to 
yield flies in late June. At this time only adult squash bugs are 
available, and upon these the flies deposit their eggs. These 
bugs are individuals which escaped parasitism the previous fall, 
and have lived to mate and lay eggs. Many of them are actively 
engaged in oviposition when attacked by the parasite, and these 
- can often complete their egg-laying before the activities of the 
maggots become fatal. One female squash bug laid a cluster of 
viable eggs just six days previous to her death from parasitism, 
showing that the metabolism of the host is not seriously un- 
balanced until late in the development of the parasite. It is this 
apparent slight effect of parasitism on the egg-laying bugs which 
has caused investigators to question the efficiency of the paras- 
tism of T. pennipes. 
While parasitized egg-laying squash bugs may be permitted 
to complete a practically normal existence, as has been shown 
above, the parasite itself may not be so well favored. Thus adult 
bugs begin to disappear from the fields about the middle of 
July, having completed the normal span of life. Parasite flies 
are actively laying eggs at this time, and often deposit them 
upon bugs which are destined to die before the parasitic larvse 
have attained full growth. In such cases the parasite cannot 
complete its development, and perishes with its host. 
Larvse which have been more fortunately situated mature 
and pass on to the pupa stage during the latter part of July and 
