June. '15] 



BISHOPP: FLIES WHICH CAUSE MYIASIS 



327 



twenty-four days. These records were also made when the tempera- 

 tures, were comparatively high. When low temperatures prevail often 

 the prepupal stage may be greatly delayed, som^etim^es lasting for 

 several weeks. 



Phormia regina, — This is the common black blow fly which is seen 

 entering houses, cellars, etc., during the cool days in late fall and early 

 spring. It appears that this species is much better adapted to cool 

 climates than those previously discussed. In fact, in the southern 

 states this form practically disappears with the coming of hot weather, 

 and is not seen again until the cooler days of autumn. At the lati- 

 tude of Dallas, specimens of this fly have been observed frequently 

 in mid-winter resting in sunny places. This species, like the others, is 

 largely a carrion feeder and after the appearance of cool weather in 

 the fall it largely Supplants Chrysomyia and the Lucilias as a scav- 

 enger, continuing to breed throughout winter. 



The adults begin depositing in seven to eighteen days after escaping 

 from the puparia. The egg stage varies much with the temperature, 

 ranging from less than twenty-four hours up to nearly four days, as 

 recorded by us. The duration of the larval stage is from four to fifteen 

 days, the pupal stage from three to thirteen days, and the total de- 

 velopmental period ten to twenty-five days. 



Calliphora erythrocephala. — This species is not abundant in Texas, 

 but is fairly numerous in the eastern part of the state. The flies of 

 this species were observed by us to begin depositing eggs in twelve to 

 seventeen days after emergence. The incubation period is twenty- 

 four hours, and the larvse begin to migrate from the food three or four 

 days after hatching. The pupal stage lasts from seven to nine days. 

 The time from deposition of eggs to the emergence of adults ranges 

 from fifteen to twenty days. 



Cynomyia cadaverina. — This is the large blue bottle fly which 

 in association with Phormia regina, appears- in Texas after the heat 

 of summer has passed. It is notorious as a frequenter of pantries and 

 cellars where it avails itself of every opportunity to deposit eggs on 

 food products of an animal origin. It is not averse to depositing on 

 smoked meat, although uncured meat, especially if cooked or becom- 

 hig rancid, seems to be preferred. The first eggs are deposited from 

 seven to twenty days after emergence of the adult; these hatch in one 

 or two days and the larvae, which are ravenous feeders, begin entering 

 the soil three to five days later. Puparia are formed five to thirty- 

 nine days after the larvae hatch, and the duration of the pupal stage 

 ranges from six to fifty-eight days, as shown by our tests. The time 

 occupied for the complete development of the insect, from egg to 

 adult, ranges from thirteen to ninety-nine days. 



