AQUATIC INSECTS 



have followed the sponges and are often found on them in 

 quiet water (Fig. 187). 



Food. — They are probably carnivorous but their food habits 

 are not thoroughly known. 



Aquarium study. — Neuropterans are secretive insects not 

 easy to obser\'e in their own homes, and the larvae are diffi- 

 cult to keep in aquaria unless running water can be arranged 

 in them. Something has been learned about them by field 

 observation and by keeping them in cages. 



Identification. — Key to genera of aquatic Neiiroptera larvae, 

 from "Fresh Water Biology," Needham and Needham 

 (Bibliography, p. 407). 



1 . Large forms with biting mouth parts. 



Alderflies, dobsons. Sialidce, p. 241. 2 



Small forms with piercing mouth parts. Spongilla- 



flies, etc. Hemerohiidce (Sisyridce) , p. 245. 4 



2. Body ending in a long median tail. Stalls, p. 241 

 Body ending in a pair of stout hook-bearing prolegs. 3 



3. Lateral abdominal filaments with a tuft of tracheal gills. 



Corydalis, p. 243 

 Lateral abdominal filaments with no tracheal gills be- 

 neath. Chaidiodes, p. 244 



4. Bristles on back of thorax sessile. Sisyra, p. 246 

 Bristles on back deviated on tubercles. 



Cllmacla, p. 245 



Family SialidcB 



Alderflies, dobsons, fish-flies 



Smoky alder fly, Sialis infumata. — Alderflies (Fig. 184) 

 were so named by the English fishermen because they settle 

 on the alder bushes which overhang the streamside; in Wales 

 they are called "hump-backs." They are he^vy, awkward 

 fliers which are easily captured; when approached they will 

 often run rather than take to their wings. 



241 



