302 THE entomologist's record. 



So far as I was able to follow them, the majority had four moults, a 

 few only attaining their full growth in the ith skin. 



The following are the chief points of difference between adult 

 LARv^ of the hybrid AND THOSE OF S. ocELLATUs. — Head : smoother, 

 and not so pointed ; yellow lines down face much broader. Bodn : 

 not so long and graceful ; the sub-dorsal stripes much weaker ; the 

 oblique stripes not so strong ; slight traces of small oblique stripes just 

 above the bases of prolegs 1 , 2 and 8 (these are altogether absent in 

 S . ocellaUUi) . Caudal horn: yellowish at upper end. Sjiirarles : not 

 so large or dark ; 1st and 2ncl pairs of prolegs are retractile, but to a 

 less extent than in S. occUatus. Resting habits differ as a rule. 



Differences between the larva of the hybrid and that of S. 

 popULi. — Head : taller and more pointed. Bndi/ : longer, and not so 

 dumpy. Oblique stripes : rather broader. As in the larva of S. ocellatus, 

 the stripes are due rather to colour than structure ; the 1st no stronger 

 than the following — 2nd to 5th ; the 7th runs forward to front of 4th 

 pair of prolegs (as in .S'. ocellatus). Small oblique lines above base 

 of prolegs present, but much fainter than in .S. pojndi. Caudal horu : 

 sky-blue in colour at base. 



In its general appearance the larva, in the 1st and 2nd stages, 

 approaches S. ocellatus rather than S. populi ; in 3rd and early part of 

 4th stages it has a greater resemblance to -S'. pojmli ; when full-fed it 

 veers back again towards S. ocellatus. 



A very similar change takes place in the larval life of >S. populi, 

 though perhaps this is not quite so marked as in the hybrid. It is in 

 the middle stages (2nd and 3rd) that this larva attains its greatest 

 distinctiveness ; in the first and last stages the difi'erence between it 

 and the larva of *S. ocellatus not being nearly so sharply contrasted, and 

 this departure and return is in no way due to the development of 

 S. ocellatus, which does not greatly differ in appearance throughout its 

 ontogeny. 



In the shape and structure of head, and the markings on its body, 

 the hybrid larvie were remarkably constant. I looked with especial care 

 for any individual variation or difference in the oblique stripes ; which 

 it seemed not unlikely might vary in the direction of .S'. populi, by a 

 strengthening of the 1st, but in no case was there the slightest 

 tendency in this direction. 



Throughout my notes I have made comparisons between the hybrid 

 larvas and those of the parent species, but with some characters the 

 agreement with S. tiliae is as close as, or closer than, that with 

 S. ocellatus and S. populi, and where this agreement is present, as, for 

 instance, in the colour of the processes at the apex of head, we have, I 

 think, conclusive evidence that this was their original appearance. 



The larvfe were very delicate, more especially during the early 

 stages, the moulting periods being the most critical of all. The less 

 robust appeared to have great difficulty in getting rid of their old skin ; 

 I assisted them oft" with their old clothes in several instances, but, alas, 

 in no case did my help prove of any avail, for they died in spite of my 

 philanthropic eftbrts. 



I suspect the difticulty really consists in drawing out the old 

 linings of the trachete, the rough assistance one is able to render 

 probably results in breaking them away from their attachment to the 

 old skin, and leaving them to clog the breathing apparatus. 

 (To he cuntinued). 



