240 



ELEMENTARY ENTOMOLOGY 



Some of the louse-flies (Hippoboscidae) are winged, though some 

 of them cast off or bite off their wings, and are frequently found 

 on birds of prey, while others are common on various birds and 



mammals. The bodies are 

 very much flattened, the 

 head is joined to the thorax 

 broadly, the antennae con- 

 sist of a single segment, 

 and the wing-venation is 

 very simple. The best- 

 known example of the 

 wingless forms is the com- 



FIG. 381. A louse-fly (Olfersia sp.). (Enlarged) mon sheep-tick (Melopha- 



gus ovinus), which should 

 be carefully distinguished from the true ticks 

 (belonging to the Arachnida), and which is the 

 only troublesome member of the family. 



A nearly related family (Nycteribiidae), look- 

 ing like small spiders, are known as bat-ticks 

 and are even more degenerate in structure. The 

 third family (Braididae) consists of a single spe- 

 cies, the bec-lousc, a minute insect about one six- 

 teenth of an inch long, which is found clinging 



to the thorax of queen and drone bees. 



FIG. 382. Sheep-tick 

 (Melophagus ovinus] 



FIG. 383. Bee-louse (Braula 



caeca) and its larva. (Greatly 



enlarged) 



FLEAS (SIPHONAPTERA) 



The fleas may be considered in con- 

 nection with the flies, for they were 

 formerly thought to be wingless Dip- 

 tera, but are now classed as a distinct 

 order. The name- of the order is de- 

 rived from two Greek words, siphon (a 

 tube) and apteros (wingless), referring 

 to the tubelike mouth-parts and the 

 lack of wings. The fleas have an oval 



body which is very strongly compressed laterally, enabling them to 

 pass through narrow cracks. They are usually of a brown color, 

 with small heads bearing sucking or piercing mouth-parts, and 



