322 THE STUDY OF INSECTS 



two are blood-sucking parasites of nestling birds. The following are our 

 best-known species. 



The blow-fly, Colli phora vomitoria, is larger than the housefly, and 

 black in color, with a steel-blue abdomen. It flies with a loud buzzing 

 noise, and lays its eggs upon meat, cheese, and other provisions. The 

 eggs hatch in about twenty-four hours, and the larvae become full-grown 

 in a few days. 



The greenbottle-fly, Lucilia ccesar, is a common species which re- 

 sembles the blow-flies in habits but it is smaller. The abdomen is some- 

 times bluish but more often greenish. 



The screw-worm fly, Chrysomyia macellaria, is a bright metallic-green 

 fly, with three black stripes on the thorax; it measures about one third of 

 an inch in length. This pest resembles the flesh-flies in habits, and it 

 deposits its eggs in wounds, sores, and the nostrils and ears of men and 

 cattle. The larva? living in these situations often cause serious sickness, 

 and sometimes even death. 



The cluster-fly, Pollenia rudis, is so-called because 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 fly slightly larger than the 

 housefly. The thorax bears many short golden hairs. Its larvae are 

 parasitic on earthworms. 



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 Calliphoridse ; but a wider knowl- 

 edge of the habits of various members of this family shows that this 

 name is misleading. 



The Sarcophagidae includes all of the Muscoid flies that agree in 

 having the following characteristics: The coloration is gray or silvery, 

 tessellated or changeable pollinose; vein M'i +2 has an almost angular 

 bend and ends considerably before the apex of the wing; the sides of the 

 face are hairy; and the arista of the antennae is plumose above and below 

 for nearly half its length or a little more. None of the species has discal 

 machrochaetae on the abdominal segments, hairy eyes, long proboscis, 

 rudimentary palpi, or more than a single pair of discal scutellar bristles. 



So far as is known all species of this family are larviparous. The 

 different species show a wide range in larval habits; but by far the 

 greater number of the species that have been bred are parasitic in other 

 arthropods. They have been bred from various insects, from scorpions, 

 and from the egg-sacs of spiders. Several species have been bred from 

 dead fish; and a considerable number from the excrement of mammals. 

 Five or six species live only in the tubular cups of pitcher-plants (Sarra- 

 cenia), feeding on the dead insects found there. It has been found that 

 Sarcophaga hcemorrhoidalis is sometimes the source of intestinal myiasis 

 in man, and several cases of cutaneous myiasis caused by larvae of Wohl- 

 fahrtia vigil have been described. 



If one wishes to determine the species of this family he should obtain 

 the monograph, "Sarcophaga and allies in North America" by J. M. Al- 

 drich, published in 191 6. 



