August, ’24] GLASER: REARING FLIES FOR EXPERIMENTAL WORK 
495 
in other words, to cover the time required for the preoviposition period, 
the insects were first fed directly on horses and cattle. This was effected 
by placing a number of newly emerged male and female flies in a wide¬ 
mouthed six-ounce bottle covered with cheesecloth and pressing the 
covered end firmly against the back or side of the host. The flies soon 
insert their mouth parts through the cheesecloth top and feed. This 
method qf feeding biting flies .is tedious, however, as the bottles must be 
held to the animals for at least a half hour to insure the engorgement 
of all the flies. When many flies are to be fed, it is almost impossible to 
do anything else during the course of the day. The horse or cow are 
partly restrained in stanchions during the operation but, nevertheless, 
often violently resent being punctured in one place by a dozen or more 
flies and this, of course, does not add to the simplicity of the procedure. 
Small fly cages attached to horses or cattle are of no value, for these are 
rubbed off as soon as the irritation caused by the feeding insects begins. 
The use of small laboratory animals, by means of the cage previously 
described, next suggested itself. This method proved somewhat better, 
provided one is fortunate enough to acquire a phlegmatic guinea pig or 
rabbit. Most of these animals, however, become extremely nervous and 
active when attacked by flies and will usually not permit them to re¬ 
main upon them long enough for complete engorgement. 
It was found that reared Stomoxys engorge readily on defibrinated, 
whole horse or cow blood when the latter is warmed to a temperature of 
35°C.-37°C. The blood is obtained under sterile conditions from the 
jugular vein of the animals, is defibrinated, and stored on ice until 
needed. A large enough amount to supply the needs for about two 
weeks is obtained at one tjme. On feeding, the serum and cellular 
element^ are mixed with a pipette, the mixture warmed and dropped 
on the breeding jar or bottle covers. 
When reared Stomoxys , in mixed sex cultures, are fed defibrinated 
blood they will oviposit from three to seven times and lay many eggs. 
These eggs hatch, develop and produce another generation of flies. 
Up to date five generations of Stomoxys clacitrans have been reared in 
this manner. 
The longevity of reared adult Stomoxys thus fed varies from 3 to 46 
days, with an arithmetical mean of 20 + days. The preoviposition 
period varies from 9 to 13 days, with an arithmetical mean of 10 + 
days. 
The sexes of bred Stomoxys are approximately equal, with a slight 
preponderance of males. No effect on the sex ratio was noticed that 
