70 
parasitic or to injurious species, while fungous and bacterial diseases 
are probably affected by still different conditions. 
Predaceous insects, as a rule, are more resistant to extremes of tem- 
perature, dryness, or humidity than all of the other insects and organ- 
isms which produce diseased conditions of insects. 
Parasitic insects were more abundant during the season of 1900 than 
during 1899, but this does not apply to all of the common species. 
For example, our two common parasites of the imported cabbage but- 
terfly, though numerous early in the season, were extremely rare toward 
the close of the year. 
Some experiments were made to test the prevalence of parasitic 
insects and fungi and their effects upon the reproduction of some 
common pests. 
The imported cabbage butterfly, Pieris rapw, was one of the species 
with which experiments were made. Larve were obtained from all 
available sources from the District of Columbia, Virginia, and Mary- 
land, and kept under the best possible conditions during September, 
1900, with the result that not a single parasite was reared, nor did this 
species appear to be affected by any disease at this time. Practically 
all of the larve used in experiments which were approaching maturity 
when placed in our rearing jars produced pup and eventually but- 
terflies. 
While on the subject of the parasites and other natural enemies of 
this cabbage pest it should be stated that Pteromalus puparum and 
Apanteles glomeratus made their appearance with the development of 
the first generation of butterflies, the Chalcidid appearing at the same 
time and the Braconid only a few days later. The wheel bug, Prioni- 
dus cristatus, does not appear to have been recorded as an enemy of 
this cabbage worm. It was many times.observed during the season of 
1900 devouring the ‘* worms.” One was observed June 23 which had 
killed a larva twice its size. 
Specimens of diseased larvee referred to the Division of Vegetable 
Physiology and Pathology in the fall of 1899 were found to be affected 
by a fungus of the genus Sporotrichum, identified by Mrs. Flora W. 
Patterson as probably S. globuliferum Speg. 
The cabbage looper, Plusia brassice.— Diseased and dead larvee of 
this species taken in the fall of 1899 and referred to Mrs. Flora W. 
Patterson, Assistant Pathologist, were identified as suffering from a 
fungus of the genus Entomophthora, doubtfully referred to sphwro- 
sperma Fres., a species which occurs upon many insects of different 
orders. 
During September, 1900, it was estimated that a little less than 20 
per cent of the larvee of this species present in the fields about the 
District of Columbia had yielded to the effects of disease usually just 
before attaining maturity. This disease was by no means general, and 
