(U7) 



358 0. GOKDON HEWITT. 



The larvae are creamy-white in colour and have a shiny, 

 translucent appearance. 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 genae are fulvous to golden-yellow and are beset with 

 black hairs, whereas in C. vomitoria the genae 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 larvae 

 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 



