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. 



. 







i - 



: 



FIG. 25. Types of insect legs 



A, grasshopper (Schistocerca tmifriariiti) ; /?, a cicindelid beetle (Cicimlfla b-i^itttata} ; C, a 

 gyrinid beetle (Dint'iitc* ritttitus) ; D, a \ oung mantis ; E, a mole cricket (Gryllotalpa borcalis) 



In aquatic forms the legs are variously developed for swimming or 

 skimming over the surface. The males frequently have the fore- 

 legs developed for grasping the females, as in the suckerlike disks 

 on the fore tarsi of the predacious diving beetles (Dytiscidac). 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 



COSTA 



8UBCOSTA 



RAVIVS 



MEDIA 



CVSITUS 



FIG. 26. Hypothetical type of wing 

 venation 



(Adapted from Comstock and Needham) 



(nearly related to grasshoppers) 

 then existed, with a wing ex- 

 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 



