ANATOMY OF INSECTS EXTERNAL 



the metatarsi bear a series of spines used as a pollen comb, and 

 the metatibiae bear a fringe of hairs on the outer surface surround- 

 ing what is called the pollen basket, adapted for carrying pollen. 



FIG. 25. Types of insect legs 



A, grasshopper (Schistocerca americana) ; , a cicindelid beetle (Cicindela b-guttata) ; C, a 

 gyrinid beetle (Dinentcs vittatus) ; >, a young mantis ; , a mole cricket (Gryllotalpa borealis) 



In aquatic forms the legs are variously developed for swimming or 

 skimming over the surface. Thejpales frequently have the fore- 

 legs developed for grasping^the females, las in the suckerlike disks 

 on the fore tarsi of the predacious diving beetles (Dytiscidae). In 

 general, insects which are strong fliers and are usually on the wing 

 have weak legs. 



Wings. Millions of years ago insects became the pioneers in 

 aerial navigation by the development of wings, which have un- 

 doubtedly been chiefly responsible for the enormous development 

 of insects as a class, living in 

 all latitudes and environments. 

 The largest existing insects are 

 certain tropical moths whose 

 wings expand nearly a foot, 

 but fossils from the coal age 

 show that immense phasmids , . 



FIG. 26. Hypothetical type of wing 



(nearly related to grasshoppers) venation 



then existed, with a wing ex- (Adapted from Comstock and Needham) 



panse of over two feet. The 



largest wings are not, however, always the most serviceable, and 

 the strongest fliers are usually of medium size. The wings pre- 

 sent a variation of structure in almost every group, and, with the 



..RADIVS 



