242 THE entomologist's record. 



egg as the anal segment was driven forward by the growing segments 

 towards the head, which remained comparatively fixed in position, I 

 asked Dr. Chapman, whose experience is so wide, to look through my 

 own notes and these, and to be kind enough to formulate his own 

 observations for me to use. This he has very courteously done, and 

 now writes : — 



" Mr. Tutt asks me to describe the phenomena associated with the 

 change of position that occurs in the young lepidopterous larva within 

 the shell before hatching. I must, in the first place, disclaim all idea 

 of being an authority on the subject, and can merely endeavour to make 

 clear what others have described, so far as my own observations have 

 enabled me to understand the subject. I have followed the develop- 

 ment of the young larva in sundry Fyralides, of which Botys hyaUnalis 

 is quite as good as any ; B. verticalis has larger eggs ; ScopuJa pnmalis 

 is fairly satisfactory for the purpose ; the transparent- egged Acronydas, 

 especially A. strigosa, afford good subjects for observation, but the rib- 

 bing of the shell somewhat obscures details ; Limacodes testudo also 

 gives a very satisfactory egg for the purpose. 



" In all cases the larva first appears on the surface of the yelk-mass 

 as a flat plate, of which the central line is the middle of the ventral 

 surface, and the margins are the two sides of the dorsum still far apart. 

 These mai-gins however rapidly curd in and, at the head and tail, the 

 young embryo soon has the cylindrical form we associate with a larva, 

 but centrally there remains a wide opening through which the mass of 

 the yelk is continuous with that portion of it contained in a central 

 cavity of the larva ; this central cavity is the future alimentary canal, 

 not yet j^rovided, however, with any opening towards either the head 

 or the tail. The communication between the intestinal cavity and the 

 yelk-sac gradually becomes smaller, and portions of yelk leave the sac 

 and pass into the intestine, and contribute to the growth of the embrj'O. 

 During this period, it is easy in flat eggs like those of the Pyralides, 

 Tortrices, Limacodes, &c., to see the embryo curled round a greater or 

 less portion of the yelk-sac, with its ventral surface towards the margin 

 of the egg, and its dorsal surface (aspect rather than surface, as the 

 surface is still broken by the umbilical opening) applied to the yelk-sac. 

 There is a little variation in the degree to which the yelk disappears 

 before the umbilical opening closes, but when this takes place the larva 

 forms a horse-shoe or circle, with the venter towards the shell-wall 

 and its anterior and posterior extremities in contact. At this period, 

 also, there are a varying number of globules of yelk free in the egg- 

 cavity around the larva ; whether these are set free by the movement 

 of the larva that now takes place, or still later by the jaw action of 

 the larva I am not sure, but after the movement has taken place the 

 young larva swallows these ; this swallowing of the remaining yelk may 

 indeed be regarded as a first step towards eating its way out of the egg. 

 Before the closing of the umbilical opening, the embrj'^o may be regarded 

 as an a})pendage to the yelk-sac, attached thereto by its dorsal aspect. 

 As soon as the opening closes, however, the young larva is truly a young 

 larva, possessing no organic connection with the other egg structures. 

 The first use it makes of this liberty is, to bend the tail forwards, and, 

 as it were, creep up its own ventral siirface, assuming in this process 

 an S or pot-hook shape, until at length its position is reversed, the 

 dorsum being now along the circumference of the egg, and the venter 



