191S.] IX 



and there is a twinkling in the upper part of the saws demonstrating 

 that thej also advance and retreat alternately. The cuticle of the 

 petioles is ver}^ minutely wrinkled, so that the view of the parts is not 

 quite so clear as in Trichiosoma^ as well as their being smaller, so that 

 one cannot always be as positive as to what one sees as in that genus. 

 It is just j^ossible that the saws advance alternately beyond the supports — 

 in fact, they cei'tainly do so ; the doubt is as to whether the other saw 

 hardly moves when its fellow advances or whether it accompanies for 

 about half the amplitude of the movement. The great difference 

 between Cladius and Trichiosoma is that in the latter the saws curve 

 round the end of the support, but do not leave it in their to-and-fro. 

 movements, and the cutting is done by the margins of the curved 

 extremities ; in Clachus the saws in their to-and-fro movements keep 

 straight, go beyond the suppoi-ts and do the penetration, but not the 

 widening of the cutting by their sharp points. 



It is, perhaps, curious that the oviposition should take place equally 

 on each side of the petiole ; it is, possibly, because it is well to make the 

 most of a suitable one ; before settling down to ovipositing, the fly 

 walked up and down the petiole and went more than once round the leaf, 

 and would a^Dpear to bite the surface close to the petiole, not, however, 

 breaking the surface ; it was probably a test as to whether the sub- 

 cuticular cell-walls were tender and at a stage at which they could be 

 easily cut by the terebra. The selected leaves were always fully 

 developed, but only just so, younger and older being refused, though at 

 this date the tree afforded few leaves that one could suppose to be over- 

 mature. This biting of the leaf as some sort of test of the j)etiole 

 reminds me of the action of the larva of Centra vinula, and of some 

 other larvae, that before beginning to eat a leaf would often strongly 

 pinch the petiole close to the leaf, but without biting it — that is, not 

 breaking the surface. 



Reigate. 



Dec. SrcZ, 1917. 



THE EMERGENCE OF TRICHIOSOMA TIBIALS FROM ITS COCOON. 

 BT T. A. CHAPMAIS^, M.D., F.Z.S. 



I reared a number of larvae of this species in hope of making some 

 further observations as to parthenogenesis in Trichiosoma. 



In the case of this species, and in Cimhex sylvarum, the observations 

 so far are that the females begin to lay as soon as they emerge, but after 

 a tune, and while still with a considerable egg-content, they refuse to lay 



