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 . CMronoinus digitatus (p. 483). 



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



Ckironomus sp. C (p. 530) . 



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



remainder of disc with short setulge which are scarcely stronger 

 posteriorly Cliironomus palliatus (p .442) . 



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



the other near apex 15 



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



Cliironomus fulviventris. 



— 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 



CJiironomus 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 setulse 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 setulse near posterior margin ; 

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

 setulse PseudocJiironomus ricliardsoni* (p. 500). 



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



— Larger species, over 6 mm. in length 19 



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



ulse, the median one broad, enclosing numerous small rounded 

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

 inconspicuous Clvironomus flavicingula (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. 



