874 



AN INTRODUCTION TO ENTOMOLOGY 



two-jointed, and in some genera lack the arista; the mouth-parts are 

 short and not at all retractile ; the win<^s are well developed in some 

 forms, in others they are vestigial or wanting ; the abdomen is indis- 

 tinctly segmented in most cases and leathery in appearance. 



Family HIPPOBOSCID^ 

 The Louse-Flies 



The louse-flies are very abnormal flies that, in the adult state, 

 live like lice, parasitically, upon the bodies of birds and mammals. 

 Some species are winged, others are wingless, and still others are 

 winged for a time and then lose their wings. 



The body is depressed ; the head is closely attached to the thorax 

 which is notched to receive it. The antennae are apparently one- 

 jointed, with a terminal arista or style ; they are situated in depres- 



^4 + 5 



2d^ ^3+<^''' 



Fig. 1118. — Wing of Lynchia. 



sions near the mouth. The legs are broadly separated by the sternum ; 

 they are comparatively short and stout; the tarsal claws are strong 

 and are often furnished with teeth. The winged forms vary greatly 

 in the venation of the wings. The veins near the costal border are 

 usually strong while the others are weak. Figure i t 18 represents the 

 venation of Lynchia. 



The sheep-tick, Melophagus ovlnus. — This well-known pest of 

 sheep is the most common member of the Hippoboscida; found in this 

 country. It is wingless and its halteres are vestigial 

 (Fig. 1 1 19). It is about 6 mm. in length, of a reddish 

 or gray-brown color, and with the entire body covered 

 with long bristly hairs. This pest is often very injurious, 

 especially to lambs after shearing time, as it tends to 

 migrate from the old sheep to the lambs at this period. 



The life-history of this species illustrates well that 

 type of development which suggested the name Pupi- 

 para for the Hippoboscidae and allied flies. The struc- 

 ture of the female genital tract is described by Pratt ('99). A striking 

 feature of it is the presence of two pairs of much branched glands, 



Fig. 1 1 19. 



