STRUCTURE OF INSECTS 



39 



number of segments and modified in a great variety of ways 

 in different groups of insects. Some of these modifications 

 may be mentioned briefly. 



The joints may be widened so as to appear toothed along 

 one margin, in which case they are called serrate. If con- 

 stricted at each end so as to appear like a string of l)eads 

 they are called moniliform; if expanded widely toward the 

 apex on one side they form a series of comb-like teeth and 

 are then said to be pectinate; if swollen toward the apex, 

 or club-shaped, they are called clavate; and if this swollen 

 portion is confined to a few of the terminal segments and 

 expanded so as to form a ball they are capitate. In moths 



C"^" 8^^^ Pall/us 

 Laliium Maxilla 



Prulhurax [lead 



Fig. 17. — Anatomy of grasshopper. (Reduced from Packard.) 



they may be provided with a series of plume-like expansions 

 on either side and are then bipectinate, or if extremely wide 

 and feathery are called plumose. 



The compound eyes are usually large and conspicuous, 

 and composed of an immense number of facets, these num- 

 bering in some insects many thousands, being especially 

 numerous in dragon flies, horse flies, and some butter- 

 flies. The ocelli are the more simple eyes, composed of a 

 single lens, and are often so minute as to be seen with diffi- 

 culty except by the aid of a lens. They may be three in 

 number, sometimes two and in some cases wanting. Usually 

 they are located between the compoimd eyes, and on either 



