DIPTERA 875 



the "milk-glands", which secrete a fluid for the nourishment of the 

 larva. The larvae become full-grown in the uterus of the female and 

 are bom one at a time at intervals of several weeks. In about twelve 

 hours after the larva is born the pupariimi is completed; and the 

 adult emerges in from nineteen to twenty-four days later. 



To control this pest the sheep should be dipped twice after shear- 

 ing, in some good "dip" of which several kinds are on the market 

 (See Farmers' Bull. 798, U. S. Dept. Agr.) 



Among the more common representatives of this family, besides 

 the sheep-tick, found in this country are the following. 



Lynchia americdna. — This is a yellowish winged species rather 

 common on owls and other raptorial birds, and on the partridge or 

 ruffed grouse. 



Lipoptena depressa.- — ^This species is found on deer. The young 

 adults are winged and probably fly about in search of their host ; but 

 later after becoming established on a deer they shed their wings. 



Family STREBLID^ 



The Bat-Ticks in part 



This family and the following one include small flies that are 

 parasitic upon bats. In this family the head is of moderate size, 

 with a freely movable neck, but is not bent back upon the dorsum 

 of the thorax, as in the following family. The eyes are vestigial or 

 wanting; the ocelli are wanting; the palpi are broad and project leaf- 

 like in front of the head ; the wings are sometimes wanting or vestigial. 



In this family, as in the Hippoboscidae, the larva becomes fully 

 grown within the body of the parent female. 



For figures and descriptions of some of our species of this family 

 see Ferris ('16). 



The genus Ascodipteron, species of which are found in the Australian region and 

 in other parts of the Eastern Hemisphere, is of great interest, because the females 

 become endoparasites. The adults of both sexes are winged at first. Later the 

 female, probably after copulation, cuts a hole through the skin of a bat and after 

 shedding her wings and legs nearly completely imbeds herself in her host. The 

 insect then increases greatly in size and becomes a flask-shaped creature, both 

 head and thorax becoming invaginated so that they are not visible. The caudal 

 end of the body projects from the cavity in which the insect lies. The larvae, 

 which become full-grown one at a time, are ejected from the uterus and fall to 

 the ground, where they pupate. For a more detailed account see Muir ('12). 



Family NYCTERIBIID^ 



The Bat-Ticks in part 



This family includes small, spider-like, wingless flies, which are 

 parasitic upon bats. The head is narrow, and when at rest is folded 

 back in a groove on the dorsum of the thorax. The eyes and ocelli 

 are vestigial; the antennas are short and only two-jointed; the legs 

 are long, and the tarsal claws of ordinary form; although these insects 

 are wingless, the halteres are present, but sometimes vestigial. 



