CLASSIFICATION AND DESCRIPTION OF COMMON INSECTS 273 



The Screw-worm Fly {Chrysomyia macellaria Fab.) occurs as far 

 north as Canada but is of importance economically in the south- 

 western States as a pest of stock. The adult is larger than the house-fly, 

 of a dark bluish-green color, with three distinct black stripes on the 

 thorax. The eggs are laid in irregular masses upon dead animals and 

 in wounds. The maggots bore into the carcass or flesh, often causing 

 death. (See Farmers' Bull. 857, U. S. Dep. Ag.) 



Blue Bottle or Green Bottle Flies. — -Two or three common species 

 of these flies occur which are also known as Blow, Green or Blue 

 Bottle FHes. 



Meat Fly, or Blue Bottle, or Blow Fly {Calliphora vomitoria Linn.). — • 

 A large blackish fly with bluish abdomen and black spines on the thorax. 

 Its eggs are laid on meat and dead animals, and each female may lay 400 

 to 600 eggs, which hatch very soon after deposition. Duration of a gen- 

 eration 22 to 23 days. C. erythrocephala Meig. is another common 

 species with a pre-oviposition period of 12-17 days, an active larval 

 stage of 3-4 days and a pupal stage of 7-9 days. 



Green Bottle Fly (Lucilia ccBsar Linn.). — Similar in habits to Meat 

 Fly, with pre-oviposition period of 1-3 weeks, active larval stage of 2-5 

 days and a pupal stage of 5-16 days. Hibernates as larva and pupa. 



Phormia regina Meig. is a large black fly seen in early spring in 

 houses, and breeds in garbage. 



Large Blue Bottle Fly {Cynomyia cadaverina Desv.) frequents 

 pantries. Lays eggs on meats — smoked, uncured and cooked. Pre- 

 oviposition period i to 3 weeks, larval period 5-40 days, and pupal 

 stage 1-8 weeks. 



The Cluster Fly {Pollenia rudis Fabr.) and Muscina stabulans Fall, 

 are also dangerous as disease carriers (see Part I). The former is 

 found in early spring and late autumn crawling sluggishly about, 

 often collecting in large numbers in and about houses. It has short 

 curly yellow hair on dorsum of thorax. Probably breeds in manure 

 and garbage. 



ANTHOMYIDiE (ANTHOMYIDS) 



Root Maggots {Phorbia spp.). — Three spec'es of root maggots are 

 commonly injurious to root crops — Cabbage Root Maggot, Onion 

 Maggot and Seed Corn Maggot. 



Cabbage Root Maggot {Phorbia brassicce Bouche). — A widely dis- 

 tributed insect, introduced from Europe. 



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