Identification Keys 221 



7. Larva with pecten not extending beyond the 



single tuft, outer two or three spines more 

 widely separated than others. Ventral tufts 

 not on cephalic one-half of ninth segment nor 

 over three-quarters as long as anal gills, which 

 are shorter than tube. Comb two rows, hav- 

 ing the secondary teeth on the spines very 

 slender. Tuft A, five; B, six to seven-haired. 



A edes. 

 Larva without above combination of charac- 

 ters 8 



8. Ninth segment with distinct ventral brush ... .9 

 Ninth segment without distinct ventral brush . 20 



9. Posterior angle of mandible heavily spined and 



produced so as to be more or less visible at 

 side of head ; or with four large stout spines 



on head ; or tube without pecten 18 



Posterior angle of the mandible never visible 

 from above ; without any other of the charac- 

 ters mentioned in the preceding paragraph. 10 



10. Pecten on breathing tube continued by ten or 



more bristles. Tuft almost at base of tube . . 16 

 Pecten not so continued 11 



11. With only two tufts on breathing tube, except 



in one case, where there are, besides the two 

 large tufts on ventral side of pecten, three 

 small tufts laterad of the pecten, and four 

 small tufts on the dorsal side of the tube. . 12 

 With more than two tufts or with four long 

 single hairs and two small tufts on tube. Never 

 tufts laterad of pecten. Antennae usually with 

 tufts in notch 17 



12. Spines on breathing tube more than eight. . . 13 

 Spines on breathing tube three to six 14 



13. Tuft over one-quarter up the tube OcJilerotatus. 

 Tuft almost at base of tube, within the pecten. 1 5 



