XI 



PHYLUM ARTHROPODA 



619 



This order includes Bugs, Water-bugs, Scale-insects, Plant-lice 

 (Fig. 519), and Cicadas (Fig. 520). Lice (Anoplura), wingless 

 parasites of mammals, are usually looked upon as degenerated 

 members of the Hemiptera. 



Fig. 520. Cicada. (After Guerin and Percheron.) 



ORDER 7. DIPTERA. 



Insects provided (except in the Fleas) with a single pair of 

 transparent membranous wings, 

 representing the anterior pair of 

 other orders. The mouth-parts are 



\ 



FIG. 521. Culex (mosquito) and larva. 

 (After Guerin and Percheron.) 



FIG. 522. Bot-fly of the horse (Gastro- 

 philus equi). a, mature insect ; b, 

 egg attached to a hair ; c, d, and e, stages 

 in the larval development. (After Brehm.) 



adapted for piercing and sucking. The prothorax is fused with the 



other segments of the thorax. There is a complete metamorphosis. 



This order includes Gnats and Mosquitoes (Fig. 521), House-flies 



