CHAPTER III 



ANATOMY OF INSECTS EXTERNAL 



Body structure. The extinct ancestors of the insects were 

 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 



FIG. 8. Types of insect antennae 



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



rionid beetle (Nyctobates pennsylvanicus) C, pectinate, or feathered, from a moth ; D, aris- 



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



fused) ; 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 



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