28 



Fresh-water Biology 



(Continued from page 26) 



7 — Rear of head constricted to form a sort of neck Acillus 



— Rear of head regularly sloping to rear Thermonectes 



8 — Cerci longer than abdomen is wide, plumose Laccophilus 



— Cerci short 6 



9— Front margin of head smooth Dytiscus 



— Front margin of head toothed Cybister 



10 — Carnivorous, with conspicuous rapacious mandibles Hydeophilidae — 11 



— Herbivorous, with short blunt mandibles 14 



11 — Abdomen with long lateral filaments Berosus 



— Abdomen with no lateral filaments 12 



12 — Abdomen depressed, parallel sided Enochrus 



— ^Abdomen convex, tapered to rear 13 



13 — Single tooth on inner edge of each mandible Hydrous 



— Two teeth on inner edge of each mandible Tropisternus 



14 — Abdomen with numerous rows of dorsal spines Haliplidae — 15 



— Abdomen with 2 rows of low tubercles or none Parnidae — 16 



15 — Spines very long; body burr like Peltodytes 



— Spines short, thorn like Haliplus 



16— Body flat 17 



— Body cyhndrical Elmis 



17 — Body subcircular; margin entire Psephenus 



— Body oval; margin notched Helicus 



Larvae of many genera, still unknown. The best account of them is by Wilson in U. S. Bureau, Fisheries 

 Bull. 39:231, 1923. 



KEY TO THE GENERA OF CRANE FLY LARVAE: DIPTERA 



1 — ^Head free; tail long, partly retractile 2 



— Head telescoped or slipped backward inside prothorax 3 



2 — Color yellow or brown _. Ptychoptera 



— Color rusty red or black Bittacomorpha 



3 — Body with numerous long spines longer than its own diameter Phalacrocera 



— Bod}'^ without such spines 4 



4 — Spiracular disc at end of abdomen surrounded by 6 or 8 lobes 5 



— Spiracular disc at end of abdomen surrounded by 5 or fewer lobes 7 



5 — Anal gills simple 6 



— Arlal gills branched Aeshnasoma 



{Continued on page 30) 



Genera 



Aeshnasoma. . . 



Antocha 



Bittacomorpha. 



Dicranota 



Elliptera 



Eriocera 



Erioptera 



Eristalis 



He.xatoma 



Holorusia 



Limnophila . . . . 



27 

 17-19 

 (24)* 

 14-16 

 5,6 

 20-22 

 12 



23 



35 



1,2,3 



PLATE H. CRANE FLY AND SYRPHUS FLY LARVAE 



Figs. Length Distr. Waters 



45 

 10 

 32 

 18 



7 



25-45 



10 



9 

 14 

 55 

 15 



NE 

 G 

 E 



NE 

 W 

 G 

 G 

 G 

 G 

 W 

 G 



lotic 



lotic 



static 



static 



lotic 



lotic 



both 



both 



? 

 both 



Genera Figs. 



Pedicia 30,31 



Phalacrocera. ... 29 



Pilaria 9-ll_ 



Ptychoptera. . . . 24,25 



Rhaphidolabis. . . 28 



Rhamphidia. ... 32, 34 



Tipula 7,8 



Tricyphona 4 



Trimicra 13 



Triogma 26 



Mostly from Dr. C. P. Alexander. • Differs by being rusty red in color. 



Fig. 33 is a rat tailed maggot, (family Syrphidse) larva of the Syrphus fly Eristalis. 



