FIELD BOOK OF PONDS AND STREAMS 



backward, and armed each with one or two strong 

 hooks or claws, 8 



— Prolegs, when present, on more than one abdominal 

 segment; if present on the last segment, then not 

 armed with single or double claws (except in gyrinid 

 beetle larvse, which have paired lateral abdominal fila- 

 ments), often entirely wanting. 9 



8 — Abdominal segments each with a pair of long, lateral 



filaments. Family SialidcB, p. 241. Netiroptera 



— Abdominal segments without long, muscular, lateral 



filaments, often with minute gill filaments ; cylindrical 



larvae, generally living in portable cases. 



Caddis flies, p. 247. Trichoptera 



9 — With five pairs of prolegs, and no spiracles at the apex 



of the abdomen. Moths, p. 257. Lepidoptera 



— Generally without prolegs ; never with five pairs of them ; 



usually with terminal spiracles ; long, lateral filaments 



sometimes present on the abdominal segments. 



Beetles, p. 261. Coleoptera 



Springtails — Collembola 



Wherever the shorelines make little bays of quiet water, 

 springtails gather in blackish patches on the surface film. 

 Thousands of them congregate there and if they are disturbed 

 the company will go up into the air like flying spray, coming 

 down again a foot or two away. They are so minute, that 

 they can jump upward like this and come down with all their 

 force without making more than a dent on the surface film. 

 Like water striders, though they live on the water surface, 

 they are thoroughly aerial insects. 



All Collembola are minute and none of them has wings. 

 Many species dwell in damp, shady places on land; one of the 

 most familiar, the snow-flea, Achorutes socialis, lives on the 

 snow. Although springtails have six orthodox walking legs, 

 their unique locomotor apparatus is on the hind end of their 

 bodies. On the fourth abdominal segment there is a forked 



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