BRANCH ARTHROPOD A; CLASS INSECT A : THE INSECTS 197 



Other abundant and interesting pond and brook insects 

 are the May-flies. The young May-flies (fig. 61) are 

 aquatic, living in streams and 

 ponds and feeding on minute 

 organisms such as diatoms and 

 other algae. The immature life 

 lasts a year, or even two or three 

 in some species, and then the 

 May-fly crawls out of the water 

 upon a plant-stem or projecting 

 rock and, molting, appears as the 

 winged adult. The adult May- 

 fly, having its mouth-parts atro- 

 phied (a few May-flies have func- 

 tional mouth-parts), takes no food, 

 and lives only a few hours or at 

 most perhaps a few days. It has 

 the shortest life (in adult stage) 

 of all insects. The female drops 

 her eggs into the water. 



Hemiptera : the sucking- bugs. 



TECHNICAL NOTE. Obtain speci- 



FIG. 61. Young (nymph) of 

 May-fly, showing (g) tra- 

 cheal gills. (From Jenkins 

 and Kellogg.) 



mens of water-striders (narrow elongate-bodied insects with long 

 spider-like legs which run quickly about on the surface of ponds 

 or quiet pools in streams), water-boatmen (mottled grayish insects 

 about half an inch long which swim and dive about in ponds and 

 stream-pools), back-swimmers (which are usually in company with 

 the water-boatmen, but which swim with back downwards and 

 are marked with purplish-black and creamy white patches), cicadas 

 (the dog-day locusts), and plant-lice (the green fly "of rose-bushes 

 and other cultivated plants). Compare the external structure of 

 some of these Hemiptera with the other insects already examined ; 

 note especially the sucking beak, composed of the elongate tube- 

 like labium in which" lie the greatly modified flexible needle-like 

 maxillae and mandibles, the whole forming an equipment for pierc- 

 ing and sucking. Obtain immature specimens of some of these 

 insects (distinguished by their smaller size and the wing-pads) ; note 

 that the metamorphosis is incomplete, the young resembling the 

 parents in general appearance. Both immature and adult specimens 

 of water-boatmen (Corisa), back-swimmers (Notonecta), and water- 



