J. W. H. Harrison 267 



colour, those from dilutata female to a dull ruby and those from autum- 

 nata females to salmon pink. It will thus be evident that cross ferti- 

 lisation in no wise altered the colour of the fertile ovum of any given 

 female from what it would have assumed on ordinary fertilisation. No 

 acceleration in emergence due to hybridity was manifested, and in both 

 instances the ova hatched in the April of the following year, when prac- 

 tically every ovum yielded a larva. 



The larvae were offered hawthorn {Crataegus oxyacantha) and dis- 

 played no hesitation in accepting it. In habits both sets resembled 

 autumnata, for they fed ravenously and showed neither wandering ten- 

 dencies nor slowness in feeding up. No tangible differences^ existed 

 between the two hybrid larvae and both are lovely creatures, only one 

 larva in the group, that of the hybrid between dilutata female and the 

 F2 filigrammana % x aw^wwmato </, surpassing them in beauty of design. 

 They possessed the pleasing soft apple green ground colour of autumnata 

 with its more or less conspicuous yellow longitudinal stripes, and upon 

 it were superimposed the reddish dorsal blotches of dilutata, toned 

 down here to a delicate ferruginous red. They pupated, one and all, in 

 early June. Since events in the two reciprocal crosses pursue different 

 courses after pupation it is best to consider the two life histories sub- 

 sequent to that event separately. 



The Fi generation of the cross between O, autumnata $ and O. dilu- 

 tata (/" . 



Before passing on, however, attention must be drawn to extraordinary 

 abnormalities in the behaviour of certain hybrid larvae, resulting from 

 the cross between Oporabia autumnata $ and 0. dilutata c^, in their 

 penultimate instar. About fourteen of these, instead of moulting nor- 

 mally, span a silken pad and thus attached themselves at the end of 

 March to twigs of the food plant where they remained for over a fort- 

 night without making the slightest endeavour to cast their skins — an 

 event usually occurring two or three days after cessation from feeding. 

 Without considering further possibilities I at once conceived the notion 

 that they were attempting to resume some long abandoned habit of 

 larval hibernation, and therefore removed most of them with the full 

 grown larvae to the cages used for pupation ; here, owing to their being 

 overwhelmed by the random silken threads spun by larvae seeking 



* Save in size in the first instar ; as the cubical contents of an ovum of dilutata are ^ 



less than two-thirds of those of an autumnata ovum any larva, hybrid or otherwise, 

 produced from the latter is bound to be larger than one issuing from the former. 



