Other blow flies occasionally attacking living animals include 
Phaenicia sericata (Meigen), the greenbottle fly, the black blow fly, 
Phormia regina (Meigen), and the secondary screw-worm, Coch- 
liomyia macellaria (Fab.). They also oviposit on wounds or sores. 
Larvae of the genus Protocalliphora are blood-sucking parasites 
of nestlings. 
FAMILY SARCOPHAGIDAE 
FLESH FLIES 
Larvae of this family feed on a wide variety of foods. A number 
of species are scavengers, feeding on dead insects, dung, and 
other decaying materials. Some species are parasitic in various 
insects. Adults are 6 to 12 mm. long; the sides of the face are 
hairy; the aristae of the antennae are feathery for about half 
their length; there are 3 black stripes on the thorax; and the 
abdomen is checkered. The larvae have their posterior spiracles 
located in a pit. 
Sarcophaga aldrichi Park., an important parasite of the forest 
tent caterpillar, occurs in southern Canada and from New Eng- 
land to the Lake States and Southern Appalachians. It suppresses 
significantly forest tent caterpillar outbreaks in the Lake States. 
Living young are normally deposited on cocoons and the larvae 
feed as scavengers on the prepupae or pupae inside the cocoons 
(355). Full-grown larvae are about 138 mm. long. The adults are 
strong, active fliers and during tentcaterpillar outbreaks may 
occur in enormous numbers, swarming over everything, livestock 
and people included. During intervals between outbreaks, the 
species is hard to find. In the Southern States, the related species, 
S. houghi Aldrich, parasitizes the forest tent caterpillar and elm 
spanworm. 
FAMILY TACHINIDAE 
TACHINA FLIES 
The family Tachinidae contains many of the most important 
species of insect parasites. All species appear to be internal para- 
sites of many kinds of insects, especially Lepidoptera, but also 
various species of Coleoptera, Hemiptera, Orthoptera, and 
Hymenoptera (629). . 
Tachinid flies look very much like overgrown house flies but 
differ in having an entirely bare bristle on each antennae. The 
maggots are clothed with minute spinules, and the posterior 
spiracles are flush with or raised from the adjacent area. 
The majority of species are oviparous, but a few give birth to 
living young. Eggs are deposited on the skin of the host, on leaves 
or other parts of plants on which their hosts feed, or on the soil. 
Living young are deposited on or under the skin of the host, on 
leaves and other parts of plants frequented by their hosts, or on 
the ground. The number of generations per year varies from 1 to 
10, depending on species and climate. 
A large number of native species and a few introduced species 
A429 
