15 
DEVELOPMENT AND INFLUENCE OF LYSIPHLEBUS TRITICI. 
Although there are several natural enemies of the “ green bug,” 
including one recently described by Dr. L. O. Howard as A phelinus 
nigritus, yet all of them seem to be of little importance as compared 
with the one minute parasitic species, Lysiphlebus tritici. It is this 
species, or what we are at present terming as such, that normally 
holds Toxoptera in check in this country, and so long as its develop- 
ment and activity are not obstructed by adverse meteorological condi- 
tions it will probably continue to control it. Indeed, so important is 
this insect and so powerful is its influence that in a short space of 
from ten days to two weeks it can overcome a most serious outbreak of 
Toxoptera, and thus save from destruction vast areas of growing 
grain. The species winters over in the field in the body of its host. 
In many cases these parasites, having been prevented from emerging 
the previous fall by the advent of cold weather, hibernate as nearly 
developed or fully developed adults, ready to emerge when the tem- 
perature rises to about 56° F. and remains there for a suflicient 
length of time. This is clearly shown by the fact that Mr. E. O. G. 
Kelly found hibernating adults at Leavenworth, Kans., on November 
13. In one lot of 50 dead, parasitized Toxoptera that had been 
washed or rubbed from the leaves of the young grain and taken from 
the mud about the wheat plants on February 28, after the winter was 
practically over, Mr. Kelly found 17 containing full-grown larvee of 
the parasite, 12 containing pupex of a light color, and 21 containing 
dark-colored pup, the latter evidently ready to develop promptly 
with the advent of warm weather. Mr. Kelly, on the same date, also 
secured a large number of Toxoptera in various stages of development 
that were hibernating in wheat fields near Leavenworth, Kans. The 
weather had been such as to preclude the possibility that these had 
been recently parasitized. Yet some of them soon began to show the 
yellowish color characteristic of Toxoptera parasitized by Lysiphle- 
bus, and adults were afterwards reared from them. This shows con- 
clusively that the Lysiphlebus parasites hibernate in advanced stages 
of development in the bodies of their host, which they have killed the 
previous autumn, and also as larve in those passing the winter from 
half to fully grown. 
The female Lysiphlebus is even more prolific than the female 
Toxoptera. Mr. Phillips has found females which had upward of 
400 eggs in their ovaries, and Mr. Kelly has reared in some cases 
206 individuals from a single mother Lysiphlebus. The eggs are 
lemon-shaped.and white. When excessively abundant this parasite 
will thrust its ovipositor into old and young aphides: of both sexes, 
including the sexual female even though previously parasitized; and 
Mr. Phillips has observed that it will even oviposit in the dead bodies 
[Cir 93] 
