CHAPTER III 



ANATOMY OF INSECTS EXTERNAL 



Body structure. The extinct ancestors of the insects w r ere 

 doubtless elongate, wormlike animals composed of a series of 

 cylindrical segments very similar in structure and with a pair of 

 jointed appendages attached to each segment. The mouth being 



A 



FIG. 8. Types of insect antennae 



A, filiform, from grasshopper (Schistocerca qmericana) ; B, clubbed, or clavate, from teneb- 

 rionid beetle (Nyctobates fennsylvanicus) ; C, pectinate, or feathered, from a moth ; Z>, aris- 

 tate, with dorsal plumose arista, from a fly ; E, lamellate, from a May-beetle (Lachnostema 



fnsca) ; F, moniliform, from a beetle 



at the anterior end, the appendages near it were developed to 

 secure and tear up the food. Thus the mouth-parts were gradu- 

 ally evolved, and the segments bearing them grew closer together 

 until they coalesced and formed a single well-defined region, the 

 head. With the development of wings the appendages of the pos- 

 terior segments were useless and soon disappeared, and the legs 

 on the three segments immediately back of the head became 



IO 



