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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. Pier is rajjce, was one of the species 

 with which experiments were made. Larvae 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 larvae used in experiments which were approaching maturity 

 when placed in our rearing jars produced pupae and eventually but- 

 terflies. 



While on the subject of the parasites and other natural enemies of 

 this cabbage pest it should be stated that PteromalMS puparum and 

 Aj>anteles 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. Pru 'ni- 

 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 larvae 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 TV 

 Patterson as probably S. globuliferum Speg. 



The cabbage looper. Phtsia hrassicce. — Diseased and dead larvae 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 sphoero- 

 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 larvae 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 



