1 10 STRUCTURAL AND SYSTEMATIC ZOOLOGY 



vae and pupae are active and resemble the imago. They 

 are nearly all vegetarian. Each family produces char- 

 acteristic sounds (stridulation). About ten thousand 

 species have been described. The representative forms 

 are crickets (Gryllus), locusts (Melanoplus\ grasshoppers 

 (Orchelimum), walking sticks {Diapheromera\ and cock- 

 roaches {Periplaneta). 



2. Neuroptera have a comparatively long, slender body, 

 and four large, transparent wings, nearly equal in size, 



FIG. 66. Metamorphosis of an Hemipter, Water Boatman (Notonecta). 



membranous and lacelike. The mouth parts are adapted 

 for biting. Among them are the brilliant dragon flies, 

 or devil's darning needles (Libelhila), well known by the 

 enormous head and thorax, large, prominent eyes (each 

 furnished with twenty-eight thousand polished lenses), 

 and scorpionlike abdomen ; the delicate and short-lived 

 May flies {Ephemera) ; caddis flies (Pkryganea), whose 

 larvae live in a tubular case made of minute stones, 

 shells, or bits of wood ; the horned corydalis (C&rydalis^ 

 of which the male has formidable mandibles twice as 

 long as the head; and the white ants (Termes) of the 

 tropics. 



