288 



BKITISH BUTTEKFLIES. 



They were very hungry, though, at the end of the time, and attacked 

 a piece of wild plum eagerly that was supplied to them. Prideaux 

 observes (in litt.) that, in nature, the larvae seem to rest on the 

 leaves ; so also do they in confinement, but, in the latter case, 

 appear to retire to a flat surface to undergo a moult ; usually they 

 feed on the edge of the leaves, at all events in their later larval 

 life; they grow rapidly, and leave their foodplant in captivity as soon 

 as the colour-changes, prior to pupation, have commenced. Raynor 

 adds that the earliest date on which he ever found R. betulae 

 larvae was on May 19th, 1904, when he beat a single one at Monk's 

 Wood, Hunts ; it was about the size of a pin's head, evidently only 

 just hatched, and he has always regarded June 25th as a medium date 

 for beating larvae of this species, although no doubt a few may be 

 obtained during the following fortnight. This supposition, he says, is 

 borne out by the fact that he has to-day (June 27th, 1907) just received 

 two dozen larvae from Huntingdonshire, and they are of almost all 

 sizes, from about ten days old to quite full-grown, some even having 

 assumed the purple-brown tint which is a mark of maturity. They 

 seem to feed chiefly by night, and prefer the tender tips of blackthorn 

 shoots. Mathew says that both in North and South Devon the last 

 fortnight in May and first fortnight in June is undoubtedly the best 

 time to look for the larvae, and they seem to prefer the little stunted 

 bushes growing by the sides of streams, or low down in hedges, to* 

 those of more vigorous growth. He says : " I think the larvae feed chiefly 

 by night, though I have occasionally seen them do so by day. They do 

 not eat holes in the leaves, but commence near the tip and eat right 

 across the leaf, consuming the mid-rib to near the base. When not 

 feeding they rest on the under surface of the leaves. Sometimes, 

 when full-grown, they are quite conspicuous, for I remember on one 

 occasion, when fishing between Totnes and Buckfastleigh, on a bright 

 hot day early in June, I was passing some sloe-bushes on the bank 

 above me, when, happening to look up, 1 saw a large larva of jR. betulae 

 on the underside of a leaf, its brilliant green contrasting strongly 

 with the deeper shade of its food ; the bush was quite twenty yards 

 off. I put my rod down and went and got it, and, while picking the 

 leaf, detected a couple more, and, in a short time, obtained more than 

 a dozen without the aid of a beating-stick, for they were all full-grown 

 and quite easy to see. I have also picked them off sloe- bushes in 

 Lustleigh Cleeve ; this used to be one of the best localities for them, 

 for the stunted sloe-bushes occurred in the little open spaces between 

 the granite boulders, and were easy to work, and the leaves, being 

 much smaller than those on a strong-growing bush, scarcely hid 

 a full-grown larva. 1 fancy that small larvae can be beaten 

 towards the end of April as soon as the young leaves begin 

 to open. I have obtained them very small early in May, 

 but, as a rule, I never tried for them until the end of 

 that month, or beginning of June, for, in their early stages, the 

 young larvae grow slowly. The larvae crawl in the usual slow slug- 

 like fashion, and do not move in jerks when fullgrown as the 

 larvae of Bithys (/urn-its do." Lewin remarks that the larvae are very 

 singular in their form, and at first sight appear like woodlice, lying 

 flat on a leaf or twig, without the least sign of feet, and when they 

 travel, their motion is more like that of a slug than a caterpillar. 



