OP WASHINGTON. 117 



them less conspicuous, and those that become more brightly 

 colored and these are, he says, commonly protected from in 

 sectivorous animals by the power which they possess of eject 

 ing acid or otherwise distasteful fluids are protected by 

 becoming more noticeable, and hence less liable to be mistaken 

 for edible species. 



I cannot believe that this explanation is the true one, as this 

 shedding of the skin affords but slight protection, if any ; and 

 after this molt, which, in fact, frequently does not occur until 

 after the food-plant has been abandoned, the larva imme 

 diately conceals itself either in earth, rotten wood, rubbish, 

 etc., or spins up, so that protection from enemies is entirely 

 unnecessary. 



Most Saw-fly larvae, also, are gregarious in habit, including 

 those in which this change is most marked, and from this fact 

 and their manner of feeding are very conspicuous throughout 

 their larval life, and are therefore of particularly easy access 

 to their parasitic and other enemies. For these reasons, I am 

 convinced that this molt has no protective significance, but 

 has its explanation in the fact that generally Tenthredinid 

 larvae remain for a long period in a dormant-larval or pseudo- 

 pupal state most of them being single-brooded. This molt 

 is analogous, then, to the one before pupation proper in in 

 sects, which in Tenthredinidae is commonly undergone a few 

 days only before the emergence of the mature insect. 



The contraction of Saw-fly larvae in the ultimate larval or 

 pseudo-pupal state is very marked, and the close approach to 

 the pupa is shown in the case of some species by the eyes of 

 the adult insect appearing as oval dusky spots on the larval 

 head. 



These larvae, then, undergo a supplemental molt preparatory 

 to the long larval hibernation, and the contracted dormant 

 larva during this period corresponds in a sense to the pupal or 

 resting stage of most insects, which is always preceded by a 

 shedding of the larval skin. 



Mr. Townsend read the following paper : 



NOTE ON THE GENERA TRIPTOTRICHA LW. AND 

 AGNOTOMYIA WILL. 



BY C. H. TYLER TOWNSEND. 



The L,eptid genus Agnotomyia was described in 1886 by Dr. 

 Williston (Knt. Am., II, 106) for a fly formerly placed in the 



