406 



Key to Pup^* 



1. Thoracic respiratory organs ending in numerous hairlike filaments 



{Cliironomus) 2 



— Thoracic respiratory organs simple, the surfaces usually covered 



with microscopic setulfe, or these organs entirely absent 20 



2. Dorsal abdominal segments with flattened macelike appendage on 



middle of posterior margin Cliironomus lohiferus (p, 431). 



— Dorsal abdominal segments without this appendage 3 



3. Very large species, 13 mm. or more in length 



Cliironomus ferrugineoviitatus (p. 446). 



Cliironomus tentans (p. 445). 



Cliironomus pJumosus (p. 447). 



— Much smaller species, not more than 10 mm. in length 4 



4. Dorsal abdominal segments with tw^o large approximated, pear- 



shaped patches of setulaB (PI. XXXIX, Fig. 9) 5 



— Dorsal abdominal segments without such patches, the surface al- 



most entirely covered with small setulae 8 



5. Apex of lateral margin of eighth abdominal segment without teeth 



or projections Cliironomus ienuicaudaiusf (p. 475). 



— Apex of lateral margin of eighth abdominal segment with distinct 



teeth 6 



6. The apical teeth projecting laterad Cliironomus dux. 



— The apical teeth projecting caudad 7 



7. The apical lateral margin with a single strong, curved tooth 



Cliironomus indisfincfus (p. 477) . 



8. Apical lateral angle of eighth abdominal segment with one ox two 



large and strong spurs, or a distinct spur on lateral margin before 

 apex (C. fulvus?) 9 



— Apical lateral angle of eighth abdominal segment with either a 



large broad process the surface of which has many distinct spines, 

 or with an apical comb of small spines or unspined 11 



9. Dorsal abdominal segments with a few long hairs 



Cliironomus fulvus? (p. 478). 



— Dorsal abdominal segments with minute setse 10 



10. Thorn at apex of lateral margin of eighth abdominal segment sim- 



ple Cliironomus fenellus. 



— Thorn at apex of lateral margin of eighth abdominal segment bifid 



' Cliironomus sp. A (p. 529) . 



11. Dorsal abdominal segments without distinct transverse bands of 



setulffif Cliironomus decorus (p. 473). 



* Species -nithout page number are not treated in text. 



t Under this heading will come a number of closely allied species, including 

 cristatiis, viridicollis, and several others, the paucity of my material preventing me 

 from arriving at a decision as to characters of use in their separation. 



