288 



curved forward ventrally, while the Chironominae are ahnost invaria- 

 bly straight. 



Imago. — See key to subfamilies. 



Keys to Genera 



# 



LARVAE 



1. Two or four permanently exserted blood-gills present on the penul- 



timate abdominal segment (PI. XLIII, Fig. 5) . .Cliiro7iomus, pt. 



— No permanently exserted blood-gills present on penultimate abdomi- 



nal segment 2 



2. Protlioracic pseudopods poorly developed (PI. XLI, Fig. 17) ; anal 



pseudopods fused, in the form of a single sessile disc whose mar- 

 gins are furnished with small hooks (PI. XLI, Fig. 12) ; anal dor- 

 sal papillae absent; terrestrial species (PI. XLI, Fig. 16) 



Cavipfodadius. 



— Protlioracic and anal pseudopods well developed, not sessile; anal 



dorsal papillae usually present and furnished with several apical 

 hairs 3 



3. Abdominal segments each with a distinct pencil of hairs on each 



side Cricotopus, pt. 



— Abdominal segments without pencil of hairs on either side 4 



4. Labium consisting of a pale rounded central piece and a digitate, 



dark, heavily chitinized piece on each side Cliironomus, pt. 



— Labium not as above, the lateral margins continuous, and not in the 



form of separate digitate plates 5 



5. Color of living larva blood-red; antennae short, not half as long as 



head, maxillary palpi long Cliironomus, pt. 



— Color of living larva green or yellowish, rarely faintly reddish .... 6 



6. Larva living within a case one end of which has a number of slender 



tentacular protuberances (PL XLIII, Fig. 9) Tanytarsus. 



— Larva free, or if enclosed the case is not as above but more in the 



form of a rough tunnel-way, and there are no protuljerances on 

 either end 7 



7. Dorsal papillae on apical segment much longer than their diameter 



Metriocnemus. 



— Dorsal papillae on apical segment about as long as their diameter. 8 



8. Antennae much more than half as long as head 9 



— Antennae not more than half as long as head 10 



9. Very small species, not more than 2.5 mm. in length ; only 2 perma- 



nently exserted blood-gills at apex of abdomen Corynoneura. 



— Larger species, usually more than 5 mm. in length ; 4 permanently 



exserted blood-gills at apex of abdomen Tanytarsus. 



*Specific identifications may be reached by using the keys tO' larvae and pupae 

 in my paper on this family listed at the end of this portion of the present paper. 



