SUBFAMILY CHRYSOMYINAE 1387 
10 days. A female may deposit as many as 300 eggs in from 4 
to 6 minutes, and a total of as many as 2,853 eggs. In captivity 
one female was kept alive for 65 days when fed upon meat, 
sugar water, and bananas and exposed to an average room 
temperature of about 80° F. (H. O. Schroeder and C. N. Smith, 
at Washington, D. C.), but the species probably does not live 
this long in nature. 
Adults of americana do not seem to be as active as some of the 
other species of blowflies. In cages they apparently prefer to 
remain motionless. In nature they have been observed feeding 
upon wounds, fresh manure, and fresh meat. It is obvious that 
they are strong fliers. Parish (19387, p. 743) found female flies 
capable of flying 9 miles. Gravid females are most: frequently 
attracted to wounds from 2 to 10 days old, according to Knipling 
and Travis (1937). Oviposition does not occur at temperatures 
of less than 65° F’. Short exposures to a minimum temperature 
of 24° F. will not kill adult females in nature, although con- 
tinued low temperature will apparently kill all adults. The 
average life cycle at Dallas, Tex., during September and October 
is 24 days, according to Laake et al. (1936, p. 21). 
According to the same authors (1936) americana oceurs in 
nature with macellarza in the ratio of 1:590, as determined in 
a study on the attraction to fresh infested and uninfested 
necrotic wounds in eattle at Menard, Tex. In standard meat- 
baited traps these authors determined that one specimen of 
americana occurred to 2,427 specimens of macellaria. 
Evidence secured by various agencies indicates that americana 
is a primary obligatory parasite which initiates most of the 
cases of external or subdermal myiasis of man or other animals 
in North America. Necrotic lesions are subject to continuous 
attack and the species has been obtained in pure culture from 
nearly 80 percent of all cases of cutaneous myiasis in Texas, 
according to Laake et al. (1936). Specimens of americana have 
never been bred from carcasses of animals in nature so far as 
I know except in instances wherein larvae occurred in the animal 
before it died, and in nature females have not been observed to 
oviposit on wounds other than those of living warm-blooded 
animals. It is the only North American ealliphorid known to be 
_ entirely parasitic upon mammals. An animal which has become 
infested with larvae of americana usually dies unless treated. 
