VIII, B, 1 Mitzmain: Stornoxys calcitrans Linnseus 45 



greatest difficulty has been encountered in attempting to keep 

 flies in a common enclosure. 



Screened stable. — In a screened stable, aside from the arti- 

 ficial conditions of confinement, the difficulties are chiefly from 

 the presence of natural enemies, and do what one may it is 

 well nigh impossible to wholly eradicate them. Particular 

 reference is made to the common insectivorous lizard and the 

 ubiquitous spider. Spraying with pure creoline was partially, 

 but not wholly effective. 



Glass vessels. — Large bottles and museum jars of a minimum 

 capacity of 3 liters were used when it was desired to confine 

 and to feed at one time a considerable number of flies. Thirty 

 days was the longest time that flies were kept in these contain- 

 ters. In this instance, it was found necessary, for the preser- 

 vation of life during the last ten days, to transfer the flies to 

 individual test tubes after feeding. 



In the use of large glass vessels, untimely death resulted from 

 mite infestation, cannibalism, and excess of moisture. 



An unknown mite, not restricted to these flies, was found to 

 be parasitic, both in the hypopial stage and in the adult form, 

 upon the flies. The first of these stages did not prove a menace 

 unless present in great numbers either on the body, which pre- 

 cluded proper functioning of the spiracles, or on the proboscis, 

 which prevented the insertion of the labium in .feeding. When 

 the mite was present as a true parasite, in the adult form, an 

 occasional one or two did not seriously affect the fly, but when 

 present in large numbers they were sufficient to enfeeble it. 



Cannibalism was encountered in the experiments to an un- 

 usual 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 might result from engorgement, in- 

 firmities resulting from broken labium, or from the wings ad- 

 hering to the glass due to an excess of moisture. I have found 

 numerous cases of flies actually fracturing the labium in at- 

 tempting to penetrate the host's epidermis, and it may result 

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

 from the container. Such a condition, of course, makes feeding 

 impossible as the proboscis is not rigid enough to puncture the 

 skin, and as a result the fly dies from starvation. 



Where a large number of flies are quartered it is difficult to 

 avoid an excess of moisture even though a bibilous filter paper 

 is employed. The condition is probably the result of excretory 



