578 



HOWARD 



on the blood of vertebrate animals, frequently causing much 

 annoyance to horses and cattle. They resemble the common 

 house fly very closely, so closely, in fact, as to deceive most 

 people. They do not frequent houses except on the approach 

 of a rain storm and late in the autumn, but they will bite human 

 beings, and the proboscis is so strong and sharp that they even 

 bite through thin clothing. The fact that they enter houses be- 

 fore storms gives rise to the common expression that, " Flies 



Fig. 27. Stomoxys calcitrans : adult, with enlarged side view of head at 

 upper left ; larva (two-thirds grown) at right ; puparium at far right ; anal seg- 

 ment of larva below, and enlarged anal spiracle of larva at lower left — enlarged 

 (original). 



begin to bite before a rain." From its biting and blood-sucking 

 habits this insect has been suspected, in common with the true 

 horseflies (all gadflies of the family Tabanid^), of carr3nng the 

 bacillus of anthrax, or ' malignant pustule,' and there is no 

 reason why it should not transfer any blood-inhabiting micro- 

 organism from domestic animals to man, or from one man to 

 another. Packard (Proc. Bost. Soc. Nat. Hist., xvi, 145) found 

 the pupa of this insect in horse dung and describes and figures it. 

 Our first experience with the breeding habits of this fly was 

 in 1889, when studying the horn fly of cattle. August 20, 

 1889, four specimens of Stotnoyxs calcitrans were reared from 

 horse manure collected at Washington, and on the 19th of 

 the same month large numbers of adults were observed by Mr. 



