AQUATIC INSECTS 



KEY TO THE ORDERS OF IMMATURE AQUATIC 

 INSECTS. NYMPHS AND LARV^. (AFTER 



NEEDHAM) 



(Collembola and Hymenoptera not included.) 



1 — Larvse with wings developing externally (nymphs) and 



no quiescent pupal stage. 2 



— Larvce proper, with wings developing internally, and 



invisible till the assumption of a quiescent pupal 



stage; form more wormlike. 5 



2 — With biting mouth parts. 3 



— Mouth parts combined into a jointed sucking beak, 



which is directed beneath the head backward beneath 



the forelegs. Water-bugs, p. 225. Hemiptera 



3 — With long slender tails; labium not longer than the head, 

 and not folded on itself like a hinge. 4 



— Tails represented by 3 broad, leaflike respiratory plates 

 traversed by tracheae, or by small spinous appendages ; 

 labium when extended much longer than the head; at 

 rest folded like a hinge, extending between the bases 

 of the forelegs. 



Damselflies and dragonflies, p. 213. Odonata 



4 — Gills mainly under the thorax; tarsal claws two; tails 

 two. Stoneflies, p. 193. Plecoptera 



— Gills mainly on the sides of the abdomen; tarsal 

 claws single; tails generally three. 



Mayflies, p. 198. Ephemerida 



5 — With jointed thoracic legs. 6 



— Without jointed thoracic legs; with abdominal prolegs, 



or entirely legless. Flies, p. 282. Diptera 



6 — With slender, decurved, piercing mouth parts, half as 

 long as the body; small larvae, living on fresh water 

 sponges. 



Families HemerobiidcB, Sisyrida, p. 245. Neuroptera 

 — With biting mouth parts. 7 



7 — With a pair of prolegs on the last segment only (except 

 in Stalls, p. 241, which has a single long median tail- 

 like process at the end of the abdomen) ; these directed 



189 



