492 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
more than once a day, but Lyperosia irritans must be provided with 
fresh food twice daily, in the morning and in the evening. Unless this 
rule is adhered to rigidly the worker will obtain an unduly high starva¬ 
tion mortality which will seriously interfere with his experiments. 
Two species of flies, namely, M. domestica and Stomoxys calcitrans , 
have been reared by the writer from approximately the middle of April 
until the middle of December. The artificial conditions (artificial heat, 
food, etc.) seem to manifest their influence at this time, however, for it 
has so far been impossible to rear these flies during the remaining four 
months of the y ear. 
The cage shown on Plate 10, Figure 5, was devised for use in feeding 
blood-sucking flies on small laboratory animals such as rabbits and 
guinea pigs. The wire gauze is the same mesh as that used for the 
breeding jar tops and will not permit the passage of a small fly like 
Lyperosia irritans. The cork closing the hole for introducing and ex¬ 
tracting the flies is shown on the top of the cage. When flies are ex- 
trated the cage is enveloped in a black cotton bag. The hair of most 
laboratory animals is very long and must be clipped in places so that the 
flies can feed. It is also often desirable to shave the skin over small 
areas. Due to the discomfort experienced by having the skin punctured 
by many flies, it is advisable not to expose the animals, at any one time, 
for more than a few minutes. 
3. Special Features 
Besides giving a few special technical hints in this section, the writer 
has also found it necessary to add a number of biological observations. 
This is not meant to include a detailed account of the life history of flies 
as this has already been accomplished by others. One cannot, however, 
work with a group of animals for any great length of time without 
noticing a few things that appear new and have been overlooked. 
M. domestica L. 
House flies have been reared by the writer from the middle of April 
until the middle of December. At this time the last generation of adult 
flies oviposited, but the progeny died either in the larval or in the pupal 
stage. These cultures were comprised of bred flies in the fifth and sixth 
generation. Whether the mortality of the cultures was due to the 
cumulative effect of the artificial conditions under which they were 
reared or not, it is at present difficult to conclude. It does not, however, 
seem to be simply a freak occurrence appearing only a single time. 
Three cultures in 1924 abruptly concluded their development in the 
manner described. 
