407 



— Dorsal abdominal segments with distinct transverse bands on some 



of the segments in addition to the normal apical one on second 

 segment 12 



12. Eighth segment without lateral apical process; all segments finely 



honeycombed. (See PI. XXI, Fig. 15, a) 13 



— Eighth segment with distinct lateral apical process; segments not 



honeycombed 14 



13. Head with 2 short conical tubercles. C/uVo?ioj)iH.9 digitatus (p. 483). 



— Head with long, apically bifid processes (PI. XXXVIII, Fig. 13) . . 



Cliironomus sp. C (p. 530). 



14. Segments 2-6 with distinct transverse band of setulffi near base, the 



remainder of disc with short setula? Avhich arc scarcely stronger 

 posteriorly Cliironomus palliotus (j) .442). 



— Segments 2-6 with 2 transverse bands of setulas, one near base and 



the other near apex 15 



15. Lateral apical process of eighth segment with 3 distinct spines. . . 



Cliironomus fulvivenfris. 



— Lateral apical process of eighth segment with more than 3 distinct 



spines 16 



16. Apical lateral angle of eighth segment with a transverse comb of 



rather short spines 17 



— Apical lateral angle of eighth segment produced into a spurlike 



process which has many small spines 18 



17. Anterior band on segments 2-6 narrow and distinct, posterior one 



also narrow but less distinct than anterior one 



Cliironomus viridis (p. 449) . 



— Anterior band on segments 2 and 3 broad, the setulse much reduced 



in size towards posterior margin of band, the band on segment 4 

 also broad and conspicuous, tapering laterally, the setulse much 

 reduced in size and very densely packed together posteriorly, seg- 

 ments 5 and 6 without a distinct band, the setula* on a large 

 rounded area from near base to beyond middle elongated and very 

 closely placed, tapering off in size posteriorly ; segments 3 and 4 

 with narrow band of rather weak setulie near posterior margin; 

 disc of segments 2-6 and anterior portions of 7 and 8 with weak 

 setuls Pseudocliironomus ricliardsoni* (p. 500). 



18. Small species, 3.5 to 4 mm. in length. .Cliironomus flnvus (p. 474). 



— Larger species, over 6 mm. in length 19 



19. Abdominal segments 2-6 each with 3 broad transverse bands of set- 



ulae, the median one broad, enclosing numerous small rounded 

 bare areas, the anterior and posterior bands narrow ; diseal hairs 

 inconspicuous Cliironomus ffavicingula (p. 432). 



*The thoracic respiratory organs are not distinguishable in my specimens. As- 

 suming that they are simple in structure, or even absent, the species will run down to 

 No. 30 in this key, when the descriptions in text will serve to separate the species. 



