DIPTERA BORBORID^E. 



45 



about bait and in soft moist earth where there is organic matter. Some 

 of them at least must have belonged to Helomyzidas, but with the excep- 

 tion of 0. fenestralis no positive identifications of larvae or pupae have 

 been made. 



The remarkable increase in numbers of Leria latens in summer was 

 mentioned before. The other species likewise increase to a certain 

 extent at the same time. L. defessa fluctuates in numbers less than the 

 other species. 



The relative abundance of Leria latens, L. defessa, and 0. fenestralis 

 in different parts of the cave is about as follows: 



The activity of these flies is affected by change in temperature. In 

 cold weather those near the mouth, where they are subject to a temper- 

 ature as low as 5 C. , become quite dormant and are scarcely able to 

 move. In summer those nearest the mouth are as active as those 

 farther in. 



Family BORBORIDAE. 

 Limosiiia tenebrarum Aldrich. 



Rep. Ind. Geol. Surv., xxi, 1896, 190 (Truett's, Donnehue's, Clifty, Marengo, and 

 Wyandotte caves); Cat. N. A. Dip., 1905, 575. 



By far the most abundant species in the cave. It is abundant in all 

 parts. During the winter it is not found near the mouth, where the 

 temperature becomes near C., and is not common from "6" to "17," 

 where the winter temperature is often quite low. But during the 

 summer it is extremely abundant near the mouth, moist places where 

 the ground is loose, the under side of rocks, and the ground under rocks 

 being sprinkled with it. On turning over a stone it hops and crawls 

 away in immense numbers. 



This fly may be expected at almost any bait or decaying organic 

 matter in any part of the cave, and where the amount of decaying 

 matter is considerable it will be found in numbers. It is not usually 

 seen in any abundance upon the wall, but is always abundant under 

 stones or other debris and occasionally becomes numerous on the wall 

 near the floor. In summer, when the part of the cave subject to consid- 

 erable seasonal change in temperature becomes warm, these flies breed 



