72 
Journal of Agricultural Research 
Vol. I, No. i 
THE ADULT PERIOD 
The fly (fig. i, a) emerges through a slit cut in one end of the pupa- 
rium and can be taken at almost all hours of the day in sweeping the 
foliage with a net. Adults put in confinement have lived io days after 
emerging, and the time elapsing between emergence and oviposition 
has varied from 4 to 10 days. The eggs are deposited soon after copula¬ 
tion and in the manner previously described. 
LENGTH OF LIFE CYCLE 
The following may be taken as the average period elapsing for the 
different stages of development during the months of June and July, 
at a latitude of 40°: 
Days. 
Time elapsing between the emergence of the adult and oviposition. . 5 
Egg period. 4 
Larval period. 4 
Pupal period. IO 
Average time for one generation. 23 
This period is considerably lengthened under existing low temperatures, 
and a maximum period of 35 or 40 days may be required in the cool 
weather of late autumn. 
NUMBER OF GENERATIONS ANNUALLY 
Since the larvae continue developing late into the autumn and many of 
them are killed by the frosts of winter, the number of generations depends 
entirely upon the latitude, altitude, and length of the growing season. 
In northern Indiana during the season of 1912 Messrs. Phillips and Lugin- 
bill recorded six generations in a series of experiments carried on from 
the time the first larvae were found in May until November. 
From field observations and generation experiments conducted by the 
junior author and Mr. E. J. Vosler at Salt Lake City, Utah, there were 
found to be at least five generations from August 1, 1911, to August 1, 
1912. The generation experiments in 1912 were started with adults 
swept from the fields in May, assumed to have issued from hibernating 
pupae. The first generation in the spring is rather well defined and 
occupies about one month. As the season progresses, the generations 
so overlap that all stages of the insect can be found in the fields at the 
same time, and the life cycle was found to be shortened to a minimum 
of 18 days. 
During the latter half of July and the month of August in the Salt Lake 
Basin it was noticed that the injured leaves of alfalfa in open fields were 
much more difficult to find than at any other time during the season. 
Moreover, alfalfa and white clover found growing in the shade were more 
generally infested than those growing in the open field. This was espe¬ 
cially noted at Laketown, Utah, August 4, 19x1, where a severe infesta- 
