188 INSECUTOR INSCITI^ MENSTRUUS 



This, then, is the larva of idahoensis. The larva described! 

 by me as above noted differs slightly. It has fewer teeth on i 

 the air-tube and more scales in the lateral comb of the eighth i 

 segment ; but the skin is spicular-pilose as in idahoensis. These : 

 differences may possibly be varietal, and, if so, then I have 

 described the larva of idahoensis. But the matter will have 

 to be looked into further. 



As to the larva of spencerii, it differs rather distinctly. The 

 skin is glabrous, or with but traces of spicules ; the comb of 

 the eighth segment has but eight teeth, each with long terminal 

 spine, longer than the body of the scale ; pecten of the air-tube 

 with 12 teeth, reaching to the middle of the tube only. 



It would appear that spencerii and idahoensis represent dis- 

 tinct species and that spencerii is absent from southern Mon- 

 tana, the spencerii-like forms taken there being aberrations of 

 idahoensis. This is the conclusion to which I was inclined 

 while collecting in Montana (see Ins. Ins. Mens., v, 119, 1917), 

 except that I thought the larvse of the two forms would turn 

 out to be alike, which is now shown not to be the case. 



