358 
(\ am? DON m<;wiTT. 
Tlie larvae are creamy-white in colour and have a shiny, 
translucent apj)earance. They are rather similar to those of M. 
domestica, but can be distinguished by the character of the 
posterior spiracles. These (fig. 5 and 6) are wider apart than 
in M. domestica and are triangular in shape with rounded 
corners; each of the corners subtends a space in which a 
sinuous aperture lies. The centre of the spiracle is occupied 
by a circular plate of chitin. The anterior spiracular pro- 
cesses are five-lobed. Under warm conditions Newstead 
found that the egg state lasted from two to three days ; 
the larval stage lasts from fourteen to twenty-one days 
and the pupal stage nine to thirteen days. There are 
three larval stages. The whole life-history may be complete 
in twenty-five to thirty-seven days. Some specimens passed 
the winter in the pupal state. 
Although S. calcitrans does not frequent to such a great 
extent asM. domestica material likely to contain pathogenic 
intestinal bacilli, on account of its blood-sucking habits, which 
cause it to attack cattle and not infrequently man, it may 
occasionally transfer the anthrax bacillus, as many have 
believed, and give rise to malignant pustule, etc. 
(7) Calliphora erythrocephala Mg. 
This is the commoner of the two English blow-flies or 
“blue-bottles.” The other species, Calliphora (Musca) 
vomitoria, is less common, although the name is frequently 
given to both species indiscriminately. They can be dis- 
tinguished, however, by the fact that in C. erythrocephala 
the genfe are fulvous to golden-yellow and are beset with 
black hairs, whereas in C. vomitoria the genm are black 
and the hairs are golden-red. 
The appearance of C. erythrocephala is sufficiently well 
known with its bluish-black thorax and dark metallic blue 
abdomen. Its length varies from 7 to 13 mm. The laiwae 
are necrophagous. The flies deposit their eggs on any fresh 
or decaying meat, nor is such flesh always dead. On one 
occasion, when obtaining fresh material in the form of wild 
