26 



Fresh-water Biology 



{Continued from page 24) 



8— Tubes open at both ends Polycentropus 



— Tubes open at one end Chimarrha 



9 — Case coiled spirally like a snail shell Helicopsyche 



— Case not so 10 



10 — Case a bored-out piece of wood Ganonema 



— Case not so 11 



11 — Case a spiral of short sticks laid lengthwise 12 



— Case not spirally wound 13 



12 — Large: length more than 20 mm Phryganea 



— Small: length less than 15 mm Triaenodes 



13 — Case square in section: made of bits of wood placed crosswise Brachycentrus 



— Case not so 14 



14 — Case of sand grains with wings at side Molanna 



— Case not so 15 



15 — Case slender with very long side pieces Mystacides 



— Case not so 16 



16 — Case smooth, conical, parchment like Setodes 



— Case not so 17 



17 — Case cylindric, bulky, showing materials and construction in great variety: a con- 

 siderable number of genera of Limnophihdas. See J. T. Lloyd — North American 

 Caddis-fly Larvae (Bui. 21 Lloyd Library, 1921) for particulars, also, C. Betten's 

 Caddis-flies or Trichoptera of N. Y. State. N. Y. State. Mus. Bull. 292. 1934. 



KEY TO THE GENERA OF BEETLE LARVAE: COLEOPTERA 



1 — Tarsal claws 2 2 



— Tarsal claws one 10 



2 — Four hooks at end of abdomen Gyrinidae — 3 



— No hooks at end of abdomen Dytiscsdae — 4 



3 — Lateral filaments of abdomen all plumose Gyrinus 



— First and second not plumose Dineutes 



4 — Abdomen with long lateral filaments Coptotomus 



— Abdomen with no lateral filaments 5 



5 — Mandibles upturned at tip to meet snout Hydroporus 



— Mandibles inturned at tip; no snout 6 



6 — Prothorax longer than head 7 



— Prothorax not longer than head 8 



(Continued on page 28) 



PLATE 10. BEETLE LARVAE 



Genera 



Figs. Length Distr. Waters 



Acilius 2, 3 



Berosus 20,21 



Coptotomus. ... 4, 5 



Cybister 15, 16 



Dineutes 11, 12 



Gyrinus (12)' 



Dytiscus 17,18 



Elmis 19 



Figs. 

 6,7 



Genera 



Enochrus 



Helichus 10 



Hydroporus 22,23 



Hydroust (14) t 



Laccophilus 8,9 



Psephenus 24 



Thermonectes. . . 1(3) 



Tropisternus. . . . 13,14 



Length 



7 



6 



7 

 22 



9 



8 

 18 

 12 



Distr. 



G 

 G 

 G 

 G 

 G 

 E 

 G 

 G 



Waters 



static 



lotic 



static 



static 



static 



lotic 



static 



static 



Mostly, from Wilson. Larvae of many genera, still unknown. 



* Differs by having the first two lateral filaments plumose, not bare, t Differs by having a single tooth on 

 the inner margin of the mandible. JSame as Hydrophilus in most of the books. 



