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 setulge, 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 ferrugiyieoviitatus (p. 446). 



Cliironomus tentans (p. 445). 



Cliironomus pliimosus (p. 447). 



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



4. Dorsal abdominal segments wdth two large approximated, pear- 



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



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



most entirely covered with small setulse 8 



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



or projections Cliironomus tenuicaudatusf (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 indistinctus (p. 477) . 



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



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

 apex (C. fulvusf) 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 fidvus? (p. 478) . 



— Dorsal abdominal segments with minute setse 10 



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



ple Cliironomus tenellus. 



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



Cliironoynus sp. A (p. 529) . 



11. Dorsal abdominal segments without distinct transverse bands of 



setul^et Cliironomus decorus (p. 473). 



*Speeies without page number are not treated in text. 



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

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

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



