286 COMPARATIVE ZOOLOGY. 
Fig. 257.—Metamorphosis of an Hemipter, Water-boatman (Notonecta). 
beak. The four wings are irregularly and sparsely vein- 
ed, sometimes wanting. The body is flat above, and the 
legs slender. The larva differs from the imago in wanting 
Fig. 258.—Seventeen-year Locust (Cicada septendecim): a, pupa; b, the same, after 
the imago, c, has escaped through a rent in the back; @, holes in a twig, where 
the eggs, e, are inserted. 
