124 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. & 



of the adult, feeding may take place at very high temperatures. 

 Below 55 degrees the flies become more sluggish and show less desire 

 to feed and dormancy appears to occur between 40 and 49 degrees. 

 Temperatures of 27 degrees are not fatal to the adults. When dormant 

 flies are placed in the direct sun they become active much more quickly 

 than when kept in the shade at the same temperature. 



The drying out of straw stacks to a depth of six or eight inches 

 largely prevents the deposition of eggs in these situations, the stacks 

 under these conditions being unattractive to the adult fly. 



Parasites and Predaceous Enemies. In the breeding of material 

 from various points in the Southwest, parasites have been found in 

 pupsB in a number of lots of Storrioxys. Two small Hymenopterons 

 of the family Pteromalidse have been found in numbers. One of 

 these is Spalangia muscce and the other is in a different genus although 

 a definite determination of it has not been made. S. muscce has been 

 bred from Stomoxys pupse collected in a horse manure pile at Welling- 

 ton, Kans., by Mr. E. 0. G. Kelly and the writer, a few specimens from 

 material collected in straw at Gainesville, Texas, and large numbers 

 from straw heavily infested with Stomoxys at Dallas, Texas. Pupse 

 obtained in rice straw by the writer at Addis, La., were also parasitized 

 but the adults have not yet emerged. In a quantity of straw kept 

 in the laboratory yard at Dallas for the purpose of breeding Stomoxys, 

 it was estimated that about 40 per cent of the pupse were parasitized 

 by these two species. This estimate was based on an examination by 

 Mr. Harry Pinkus and the writer of all the pupsB in the straw, which 

 numbered some 2500. In breeding experiments it has been determined 

 by Mr. Pinkus that parasitism always takes place in the pupal stage. 

 Both of the parasites have been found to attack the pupa of the house 

 fly {Musca domestica) and the horn fly (Hoematobia serrata), as well as 

 other mucid pupse. 



During the outbreak of this insect predaceous insects were present 

 in large numbers. Adults of Stomoxys were found to be captured 

 by several species of Asilidse which were present in great numbers 

 around straw stacks. Several species of spiders were observed in the 

 act of capturing and devouring adult flies. Two or three species 

 of mites were also found to be enemies of the immature and adult 

 stages of Stomoxys. In manure and straw histerid beetles were 

 among the more important predators. Chickens and other domestic 

 fowls, hogs and mice were found to destroy the larvse and pupse of this 

 insect in great numbers. The chickens and hogs were attracted to the 

 straw stacks mainly by the presence of grain, but they evidently 

 devoured large numbers of the immature stages of the fly while 

 searching for grain. 



