INVERTEBRATES OF THE CAVERN 179 



light could enter. With the skeleton of a great horned 

 owl found near the entrance of Yeitso's Den, at the 

 extreme limit of all traces of outside light, were found 

 numbers of the pupa cases of the blow fly maggots, 

 identified as of the genus Calliphora and probably of 

 tins species. Thus it is evident that these flies were at 

 home and breeding in the cave, although none was 

 found outside, where dozens of the common black 

 blow-fly (Phormia regina) were breeding in the carcass 

 of a dead colt not far away. These blue-bottle or blow- 

 flies are common winter inhabitants of the southern 

 part of the United States, where they breed in animal 

 carcasses. It is possible that they may breed, or 

 aestivate, in the cool caverns during the heat of summer 

 and remain in the open during the colder seasons. 



Seven other species of small flies were collected in 

 the cave, apparently all associated with the great 

 deposits of bat guano, and most of them attracted to 

 fresh meat used as a bait for such insects. Of these 

 were several specimens of tiny dung-flies (Leptocera 

 atra Adams) and two other specimens that may repre- 

 sent different species. Two specimens of a little moth- 

 fly or sewer-fly (Psychoda), species not determined, 

 were collected, one of these near fresh meat used as 

 bait. These are scavenger flies and were probably 

 breeding in wet places in the guano. Another little 

 cave dung-fly (Helomyza pectinata Lw.) was collected, 

 and might well be common in the cave, as other mem- 

 bers of the family have been^ reared from bat, rabbit, 

 and bird dung. 



Another tiny and very active little hump-backed fly 



