148 Correspondence. [j a u n 



but the legs have been the only parts not invaded so far as my observation 

 goes. The maggot eats a burrow or chimney into the flesh of its victim, 

 remaining stationary and feeding upon the fluids of the helpless messmate 

 until death releases it, when the horrid thing deserts the lifeless carcass and 

 if not destroyed buries itself in the earth. Very little seems to be known 

 about this strange fly, so far as my inquiries have extended, but the old- 

 timers call it the "screw fly," and regard it with great disfavor. 



A number of years ago a lady brought her six-month-old infant to me 

 for examination and relief, stating that whilst wheeling her baby through 

 the park it suddenly cried out as though in pain, and she discovered one 

 of these screw flies dashing about over the child's face. An investigation 

 revealed some six or eight microscopic larva? busily burrowing into the 

 tender skin of the helpless victim. And this was within half an hour after 

 the attack of the fly. 



In order to get some reliable data in regard to the genesis of this maggot, 

 I secured a number of them and bedded them in earth, confining the recep- 

 tacle in which they were to pass through their mysterious transformation 

 in a box covered with close-woven wire netting which effectually pro- 

 hibited the escape of the fly. 



Within a few days' time the larva? were transformed into the chrysalis 

 state, and in about three weeks two flies appeared, smaller than the ordi- 

 nary green fly but resembling it in every way. These flies died before I 

 could carry out further experiments, but other hatchings I trust will give 

 me the desired opportunity of watching them sting a live bird. 

 • Dr. J. Bequaert of the American Museum of Natural History, to whom 

 the dead flies were submitted, reports as follows: 



"The flies obtained by Dr. Arnold from bird-infesting maggots belong 

 to the genus Protocalliphora of the Calliphorina* or bluebottle flies. In 

 Europe and North America the larvae of two very closely allied species of 

 Protocalliphora are known to parasitize birds. The species reared by Dr. 

 Arnold from skin-boring maggots I consider to be the true Protocalliphora 

 azurea (Fallen). In the Eastern United States (Pennsylvania, New York) 

 and also in Europe there is an apparently different species, Protocalliphora 

 sordida (Zetterstedt), whose maggots live among the feathers of young or 

 even adult birds, sucking blood at intervals without boring into the skin. 

 The life history and distribution of these two bird parasites are not yet 

 completely known, and I should be very grateful for further information 

 on the subject, especially if accompanied by maggots or flies." 



Fewer maggot infested birds were brought to the hospital the past sum- 

 mer than during the previous few years. 



Careful experiments proved positively that the fly would not deposit 

 its eggs or larvae in the dead carcasses of birds. 



\\. W. Arnold, M. D. 



Rooms 5 and 6, First Nat. Bank Building, 

 Colorado Springs, Colo. 



