870 A N INTROD UCTION TO ENTOMOLOG Y 



provisions. The eggs soon hatch and the larva; develop rapidly. 

 There are several species of this genus in our fauna ; all of them have 

 reddish palpi; bluish black, opaque thorax; metallic blue or green, 

 more or less whitish pollinose abdomen; two or three posthumeral 

 bristles; and black legs. There are two common species Calliphora 

 erythrocephala, in which the bucca is reddish brown and the beard 

 black; and Calliphora vcnnitoria, in which the bucca is black and the 

 beard reddish. 



The large bluebottle-fly, Cynomyia cadaverlna. — This is a com- 

 mon species which resembles the blow-flies in size and in habits; it 

 differs from them in that the abdomen is without silvery pruinosity, 

 and there is only one posthumeral bristle on each side. 



The greenbottle-fly, Lucilia ccusar. — This also is a common species, 

 which resembles the blow-flies in habits; but it is smaller and its 

 cheeks are bare. The abdomen is sometimes bluish but more often 

 greenish. 



The screw-worm fly, Chrysomyia macelldria. — This is a bright 

 metallic-green fly, with three black stripes on the thorax, and a yellow 

 face. It measures from 8 to lo mm. in length. It lays its eggs on 

 decaying animal matter and also in wounds, sores, and the nostrils 

 and ears of men and cattle. The larvse living in these situations often 

 cause serious sickness, and sometimes even death. This is a widely 

 distributed species ; but it has attracted most attention in the South- 

 western States where it is a serious pest of stock. 



The cluster -fly, Pollenia rudis. — The cluster-fly is so-called be- 

 cause of its habit of entering houses in the autumn and hiding away 

 in protected nooks in large groups or clusters. It is a dark colored, 

 slow-moving species, slightly larger than the house-fly. The thorax 

 is thickly beset with soft woolly hair in addition to the bristles ; the 

 abdomen is brown with white pollinose spots. 



The calliphorid parasites of nestling birds, ProtocalUphora. — Two 

 species at least are found in our fauna, P. avium and P. splendida. 

 Both of these have been found to be external blood-sucking parasites 

 of nestling birds, often causing the death of the nestlings. Plath ('19) 

 found that of 63 nests of five species of birds studied by him 39 were 

 infested. 



Family SARCOPHAGID^ 



The Sarcophagids 



This family has been commonly known as the flesh-flies because 

 some of them lay their eggs in bodies of dead animals, resembling in 

 habits the blow-fly, which belongs to the family Calliphorida ; but 

 a wider knowledge of the habits of various members of this family 

 shows that this name is misleading. 



The Sarcophagidge as limited by Aldrich ('16) in his monograph 

 of the North American species includes all of the Muscoidea that 

 agree in having the following characteristics : The coloration is gray 



