character in the retention of the dorsal head-piece, and on dehiscence 

 the head-coverings remain in one piece. It is of little use for me to 

 describe the Lasiocampid pupa, since its general features must be 

 known to all entomologists. It is of stout and robust form, usually 

 rounded at both ends, and rarely gradually terminating in an anal 

 point, although this character is distinct enough in Malacosoma. 

 Ventrally the most noticeable point is the presence of the labial 

 palpi. The third pair of legs is always covered by the wings. The 

 covering of hairs — short bristly points — that thickly studs certain 

 parts of the pupal skin, often, owing possibly to the movement of the 

 pupa in the cocoon, becomes covered with a thick coating of felt-like 

 material, which gives the pupa a very strange appearance. This 

 peculiarity is particularly well marked in pupae of E. quercifolia and 

 E. ilicifolia. It is necessary here, perhaps, to point out that many 

 people ally the Notodonts with the Lasiocampids, because of the con- 

 siderable resemblance that exists between their pupae ; and even so 

 good a student as Bacot insists that the resemblance is really more 

 than a superficial one, and denotes an actual relationship. The 

 cremaster of the Lasiocampid pupa is very striking. There are no 

 curved hooks, but a thick brush of short, stiff, bristly hairs, like a 

 cocoa-nut mat. In a few species the bristles are wanting, and the 

 cremastral area is quite smooth. 



The imagines of the British species are known to all of you better 

 perhaps than to me. You are all aware of the marked sexual 

 dimorphism that exists in every species, and know that certain species, 

 such as Pivcilocampa populi, Cosmotriche potatoria, Malacosoma neustria, 

 and Eutricha quercifolia, sometimes abound at light. You know also 

 the amazing power that the females of Macrothylacia ruin, Lasiocampa 

 quercfis, and L. trifolii have of attracting males from a great distance, 

 and have seen, or at least heard of, them crawling in dozens over a 

 box in which a female has been confined. 



You all know, too, that only on one occasion (or at most two) has 

 the imago of M. castrensis been seen wild in this country, and that 

 no one knows its habits in a state of nature ; nor have I ever heard 

 of more than one or two entomologists who have seen wild in the 

 hedges an imago of Eriogaster lanestris. This is very remarkable, 

 and shows that we have not yet learned everything ; and were it not 

 for the fact that P. populi and Jlf. neustria come to light, how few 

 of these would be seen in the imago state ! 



Probably the most interesting of all our British species is Lasio- 

 campa quercus. This interest has arisen from the difficulty that has 

 occurred as to whether one of its forms or offshoots — callunce — has 

 or has not undergone sufficient differentiation to enable it to be 

 called a distinct species from, or a local race of, L. quercfis. 



Many entomologists will know that 1 have recently, in my 

 Presidential Address to the members of the City of London 

 Entomological Society, pointed out, among many other things, how 

 " isolation by diverse habits " may aid in the differentiation of species 



