130 SANITARY ENTOMOLOGY 



segment, as in almost all orders of insects. Tlie ninth and tenth seg- 

 ments are apt to be small and obscure and center around the anus, which 

 belongs to the tenth. 



The larval period varies in response to climatic stimuli, but under 

 favorable conditions is about four days in length. When full grown the 

 larva varies from 10 to 12 mm. in length. Pupation takes place within 

 the last larval skin which shrinks and hardens to form a reddish case or 

 puparium. This period lasts from 3 to 10 days. When the fly is ready 

 to emerge it pushes off the cap or head end. The entire developmental 

 period may require from eight to eighteen or more days. Kisliuk has 

 found pupae of the fly in manure piles at various times during the win- 

 ter, which of course indicates that the developmental period may occupy 

 an entire winter if the pupa is caught by cold weather. Bishopp, Dove 

 and Parman found that adults emerged from immature stages which had 

 been in manure for six months. Hutchison's observations at Washing-ton, 

 D. C, confirm these findings. 



The adult flies are capable of considerable flight. Parker demon- 

 strated a migration of two miles in his Montana studies. Bishopp and 

 Laake (1919) record the flight of marked house flies of thirteen miles. 

 In this connection the most interesting contribution is that of Ball 

 (1918) in which he shows that house flies apparently migrated with the 

 wind from 46 to 95 miles from mainland to a tin}^ island. 



The house fly has been found breeding in horse manure, human excre- 

 ment, and hog manure very freely and to some extent in cow and chicken 

 manure. It lays its eggs in a great variety of decaying animal and 

 vegetable materials, such as slops, spent hops, moist bran, ensilage, 

 rotting potatoes, dead animals, excreta-soiled straw, paunch contents of 

 slaughtered animals, soiled paper and rags, etc. 



THE BLUE BOTTLE FLIES OF THE GENUS CALLIPHORA ^ 



The large blue bottle fly, Calliphora vomit oria Linnaeus (plate I, 

 fig. 1) and its near relative C erythrocephala Meigen are often found in 

 houses. These flies have also been shown to be dangerous insects because 

 of their ability to transmit disease. In fact they are much more likely 

 to directly transmit disease organisms than the house fly because of 

 their habits of breeding in flesh which gives them also the name blow flies. 

 The adults are grayish on the thorax and dark metallic blue with sug- 

 gestions of silver on the abdomen. In vomitoria the genae are black and 

 beset with golden red hairs, while in erythrocephala the genae are fulvous 

 to golden yellow and beset with black hairs. 



' An appeal has been made to the International Commission for Zoological Nomen- 

 clature for the retention of Calliphora in this sense with vomitoria as type. 



