512 MITZMAIN. 



it was found necessary for the prolongation of life during the 

 last ten days to transfer the flies to individual test tubes after 

 each feeding. In this method with the use of glass vessels 

 untimely death resulted from mite infestation, cannibalism, and 

 excess of moisture. 



Mite infestation. — An unknown mite, not restricted to these 

 flies, was found both in the hypopial stage and in the adult form. 

 The first of these stages did not prove a menace unless present in 

 great numbers either on the body, thus precluding proper func- 

 tioning of the spiracles, or on the proboscis, which prevented 

 insertion of the beak in feeding. When the mite was present 

 as a true parasite in the adult form, an occasional one or two 

 did not affect the host, but when present in larger numbers 

 they were sufficient to enfeeble the fly on account, no doubt, of 

 lowered resistance brought about by the artificial environment. 



Cannibalism. — Newstead(57) calls attention to a case of canni- 

 balism in Stomoxys calcitrans. I have found it prevalent to an 

 unusual degree. Often the disability of an individual fly attracted 

 the attention of another more active member which promptly 

 attempted, and usually succeeded, in puncturing the helpless fly's 

 abdomen. This disability resulted from engorgement, infirmities 

 resulting from broken labium, or from the wings adhering to 

 the glass, due to an excess of moisture. Numerous cases of flies 

 have been found actually fracturing the labium in attempting 

 to penetrate the host's epidermis. This may result also from 

 the fly pricking at the glass in attempting to sip moisture from 

 the container. Such a condition, of course, makes feeding impos- 

 sible, as the proboscis is not rigid enough to puncture the skin ; 

 and, as a result, the fly dies. 



Excess of moisture. — Where a large number of flies are quar- 

 tered together, it is difficult to prevent an excess of moisture, even 

 though a bibulous filter paper is provided. The condition is the 

 result of, first, excretion ; and, second, probably, condensation of 

 the moisture of the air in the bottle, when at the temperature 

 of 20° to 26° C. 



The use of individual glass tubes. — By the use of individual 

 glass tubes the difficult problem of keeping the flies alive in 

 captivity was most successfully solved; for the flies can be ob- 

 served at all times and longevity is increased to approach the 

 normal. Ninety-four days was found to be the maximum life of 

 adult Stomoxys kept individually under laboratory conditions in 

 glass tubes. 



A test tube of 24-millimeter bore, plugged with cotton^ was 



