46 THE CANADIAN ENTOMOLOGIST. 



limits the primary setae iv. and v. I can find no trace of any small 

 tubercles, single-haired or otherwise, in proximity to the spiracle or these 

 warts. I may here remark that the ist stage oi P. trifolii shows a much 

 more primitive condition than that of Z. guercus, the warts being smaller 

 and bearing fewer hairs, while the absence of any secondary hairs arising 

 from the general skin surface obviates the difficulty of discriminating 

 between primary and secondary characters that one finds in the last named 

 species. Had I not examined the larva of P. trifolii I should not have 

 written " iv. + v. almost post-spiracular " with regard to Z. quercus, as 

 without this key, any of the numerous secondary hairs in proximity to the 

 spiracle might be taken for either iv. or v., or single hairs might have been 

 chosen for both and the large wart designated as a secondary character. 

 Unless, therefore, my eyesight is greatly at fault we must either consider 

 iv. and v. to be included within the subspiracular wart of P. trifolii, and 

 by analogy within tiiat of L.querms^ox conclude that one of them has been 

 lost ; and, in view of what Dr. Dyar has said in regard to the possible loss 

 of V. in the Sphinges and what we know as to the ready tendency of iv. 

 and v. to become members of a common group of sette in certain groups 

 of larvae, and the ])ossibility of their becoming consolidated on a single 

 segment of a larva of one species or tribe (see previous remarks re Hyles 

 ( Deilephila) euphorbice), tiie line of least resistance is surely greatly in 

 favour of the first-named conclusion. My slide showing a ist stage larva 

 of P. trifolii is at Dr. Dyar's disposal should he care to examine it. 



On the (juestion of whether the first stage of Aglia tan is to be 

 considered a specialized one, I must join issue with Dr. Dyar on two 

 points: firstly, as regards the very restricted meaning attached by him to 

 the words " Primitive first stage." This would bring the first skin larvae 

 of such species as Staiiropus fagi and Dicramira vinula within the 

 category of having a primitive or unspecialized first stadium. Even if it 

 were possible to get a majority of entomologists to accept this sense, it 

 would still be entirely at variance with the sense in which these words 

 would be understood by biologists at large. Secondly, even if we accept 

 the special meaning in which Dr. Dyar uses the term, the condition 

 implied is >iot present in the ist instar of Aglia tau. Not only are the 

 large horns identifiable with tubercle i. on the meso- and meta-thoracic 

 segments and the transversely conjoined i.+i. belonging to the 

 right and left sides of the 8th abdominal segment bear set^e on their 

 lower lateral branches, besides those on the terminal forks, but the raised 



