Contribution to the life histoiy of Orina tristis. 251 



occupy this region ; that they are in the alimentary canal 

 seems almost certain, as they escape by the mouth when 

 the larva is subjected to pressure. 



The other circumstance connected with moulting that 

 seemed to me curious, is no doubt so, only because my 

 experience in watching the moulting of iarvge has been 

 almost entirely amongst the Lepidoptera ; in these, the 

 larva always completely voids the alimentary canal at a 

 moult. A newly-moulted larva has no food contents at any 

 stage. In 0. tristis the anterior part of the alimentary 

 canal contains no food, but the hinder portion, in several 

 loops, in the abdominal segments, is more or less loaded. 

 The effete larval skin appears to be held in place so that 

 the larva may crawl out of it by a more or less half-dried 

 faecal deposit glueing the anal extremity to the leaf. 



The rupture in the larval skin divides the head into two 

 lateral (epicranial ?) pieces, and the clypeus with the mouth 

 parts and slits down the thoracic and two first abdominal 

 segments dorsally as if along a dorsal suture ; the third 

 abdominal segment is often slit in the same way, and I 

 have once seen the fourth slit also, but irregularly towards 

 one side, as if any dorsal suture was here certainly absent, 

 as it probably is in the third abdominal segment. 



At the moult to pupa the skin collapses, and so far as 

 can be judged by the condition of the cast skin the process 

 of moulting is very similar to that in Lepidopterous larvse. 



The eggs are not absolutely uniform in size and shape. 

 Their length is about two-and-a-quarter times their width ; 

 their sides are not quite straight but curved, so that the 

 middle of the egg is the widest part ; sometimes the 

 longitudinal section is an ellipse, at others there is some 

 tapering towards one or both ends (as in the small end of 

 an egg). 



The actual dimensions of four eggs measured was : — 



Long . . 2-15 . . 2-25 , . 2-25 . . 2-32 mm. 

 Wide , . 1-0 . . 0-94 . . 1-01 . . 0-97 mm. 



It is to be noted, that as the embryo is always developed 

 with the head to tlie free end of the egg, and has already 

 advanced in its development so far as to already have its 

 head to that end when laid, the orientation of the embryo 

 in the egg must be determined by its relations to the 

 ovarian tubuli in which it develops, and as these are coiled 

 in all directions, gravity has no share in the determination. 



