20 BULLETIN 766, U. S. DEPARTMENT OF AGRICULTURE. 
Constantly flying; copulating; larvipositing freely and feeding. 
(2) Actwe. Flying a little; larvipositing some; crawling around and 
feeding. (3) Jnactive. Crawling around; no copulation or larvipo- 
_ sition; very little feeding. (4) Very inactive. Practically dormant, 
sluggish. 
SEASONAL HISTORY. 
PRESENCE IN FIELD AND NUMBER OF GENERATIONS. 
Compsilura occurs in the field, as shown by collections of adults 
in 1915,on May 1. It was on this date that two male specimens were 
collected. The latest that adults were taken in the field was October © 
28 and 29, 1915. This represents the extremes of collections ‘of 
adults of this parasite. The earliest collections of puparia in the field 
were made June 16, 1915, from brown-tail moth “spin-ups,” and the 
latest record, from a collection of Pontia rapae, made September 30, 
1915. Among collections of host material for Compsilura is that of 
brown-tail moth “ spin-ups ” and the time of occurrence of these in the 
field varies from year to year, the average being about June 25. In- 
mediately following these is begun the collection of gipsy-moth 
larve for this parasite. Figuring on the foregoing basis of collec- 
tions, and allowing a range of 28 to 30 days for completion of life 
history in the field, it will be found that three full generations are 
passed during the season. 
In the laboratory the period from adult to adult averages 24 days, 
and with a “ gestation period” of 4.5 days, the life cycle involves 
about the same length of time as is required under natural conditions 
in the field. It was found possible to secure more than three genera- 
tions annually in the laboratory by supplying hosts later than they 
could be found in the field. 
The most accessible host in the spring is the brown-tail moth larva, 
which is attacked soon after emergence from the hibernating web. 
The growth of the parasite in this host during the early part of the 
larval period is more or less retarded owing to the slow spring devel- 
opment of the young brown-tail meth larve. Just previous to pupa- 
tion of the host, while the brown-tail moth larva is spinning its 
cocoon, the parasite larva emerges and pupates within the loosely 
woven web. A short time after this the appearance of adult Comp- 
silura is noted, and puparia are to be found in the early gipsy-moth 
larvee, some few coming from the late fourth and early fifth stage 
hosts. These are evidently part of the same generation as those from 
the brown-tail moth larve. The early issuing adults emerge from 
the brown-tail moth hosts in time to attack the later stages of the 
gipsy-moth larve together with native hosts, which are prevalent 
at this time, and this constitutes the beginning of the second gener- 
ation of Compsilura. Those issuing from this second generation the 
