DIPTEROUS LARViE 53 



that it deposits eggs instead of living larvae. After hatching the manner 

 of attack and the effect upon infested meat and wounds is much the 

 same and calls for the same treatment. 



Family VI. (Estrid^ 



Diptera (p. 23). Botflies, warble flies. The head is large, bearing two 

 faceted eyes widely separated, antermse short and sunken into pits in 

 the front of the head. The mouth parts are rudimentary, most all of the 

 flies living in the adult stage without food. The body is heavy and 

 somewhat hairy. The coloration is usually inconspicuous. 



The larvae are thick and twelve-segmented, the first two segments 

 not always distinctly separated. There is no demarcation into body 

 regions, only a cephalic and anal end can be distinguished. The body- 

 segments are frequently provided with rows of spines. Buccal hooks 

 may or may not be present. Tracheal openings are at the posterior 

 extremity. 



The larvae are parasitic in the stomach and intestines, mucous mem- 

 branes, subcutaneous coimective tissue, nasal passages, and sinuses of 

 facial bones of mammals; other parts are also invaded by their migrations. 

 When completely developed the larvae leave these locations in the host 

 and pass to the groimd where they enter the pupal stage. 



The flies of the family (Estridse are of world-wide distribution. 



Gastrophilus intestinalis (G. equi). CEstridae (p. 53). The horse 

 botfly (Fig. 28, h). The body of the female is one-half to five-eighths of 

 an inch in length and is very hairy. The head, thorax and abdomen are 

 brown. The wings are transparent with dark spots, those near the center 

 passing entirely across the wing transversely. The abdomen is rather 

 long and tapers to a point. In the males, which are rarely seen, the 

 abdomen is Hght brown or yellow, and it is not tapering. In other re- 

 spects the males closely resemble the females. 



The larvae (Fig. 28, c, d and g) when full grown are about three- 

 fourths of an inch ia length. At the head- extremity are two buccal 

 hooks by which attachment is made to the gastric mucosa (Fig. 28, e). 

 The body-segments are bordered by short spines (Fig. 28, d). 



Habits.' — ^Like other members of the CFstridae, the horse botfly at 

 maturity is extremely active, flying chiefly during the warmest and 

 brightest days of the summer, and generally frequenting pastures in 

 the vicinity of woods. It is the habit of the female to hover near the 

 horse with its long, pointed abdomen bent downward and forward. The 

 fly then darts toward the horse, deposits its egg, retreats, and again 

 hovers until ready to repeat the operation. The eggs (Fig. 28, a and b) 

 are yellow in color, about one-sixteenth of an inch in length, and tapering 

 toward the attached end, the free end being provided with an operculum 

 which is set obliquely and gives to this end somewhat of an obliquely 



