248 THE BLOWFLIES OF NortH AMERICA 
seven or eight branches, and Knipling (1936) found this num- 
ber to be from four to six in the North American form. 
Mr. Knipling sent to me the following summary of his exami- 
nations: ‘‘A comparison of the immature stages of the Aus- 
tralian cuprina and the American species known under that 
name indicates close relationship. However, recognized Ameri- 
can species possess no greater larval difference than these that 
differentiate these two forms. On the basis of the taxonomic 
differences discussed in this report (anterior spiracles, tubercles, 
and spines) it is concluded that the Australian and American 
forms are distinctly different. Whether or not the observed 
differences are of specific or varietal significance can be judged 
better by considering the larval differences in conjunction with 
adult differences. ’’ 
Phaencia cuprina (Wied.) is the most important blowfly in 
Australia. Approximately 90 percent of all ‘‘strikes’’ of sheep 
in Australia are due to this species according to Mackerras and 
Fuller (1937). The species is said to cause a loss of several 
millions of dollars each year to stock-breeders in that country. 
It is practically the only species to initiate ‘‘strike’’ in sheep in 
the Canberra District during the warmer months, and its distri- 
bution extends well into the drier sections of Australia. It 
reaches its greatest abundance in the tropical and arid parts of 
Australia during the spring and autumn months according to 
Mackerras, who considers the species an introduced one into 
the country. Fuller (1932) found the larva of cuprina to differ 
from that of sericata in having the posterior spiracles rounded, 
smaller, the peritreme thicker and wider ,and the slits shorter 
and wider. 
In South Africa the form usually considered under the name 
of cuprina is of little or no real economie significance so far as 
published records indicate. Lewis (1933) reported upon a num- 
ber of myiasis cases in sheep; both this species and Muscina stabu- 
lans were reared from one of these cases. Rearing of the latter 
species, in cases of myiasis, indicates that the wound was an old 
and suppurating one. Cuthbertson (1933) stated that this form 
is common everywhere in Cape Colony, South Africa, and that 
it is considered a nuisance in buteher shops and about abattoirs. 
It appears that the African form resembles pallescens of North 
America in biology and habits. 
It has generally been considered that Phaencia pallescens, 
cuprina and sericata are closely related. While several characters 
of chaetotaxy place the species together, sericata is very distinct. 
According to Heim de Balzac (1937), Villeneuve is inclined to 
