136 BRITISH LEPIDOPTERA. 



almost as quickly as those found later, were so much longer in pro- 

 ducing the perfect insect, Robson writes : " All were exposed to the 

 same conditions after capture, and I should have expected them to 

 have remained about the same time in the pupal stage, yet the 

 earlier found larvae required from 53 to 64 days to produce 

 imagines, and the later ones only 21 to 35 days, the first lot 

 being therefore almost 3 times as long in the pupal condition as 

 the second." Robson says that this suggests a bearing on the impossi- 

 bility of forcing at once fullfed autumnal larvae, and that the latter, 

 though fullfed, may not be mature, and probably require considerable 

 time for certain internal changes to take place before they can go 

 on, and that such fullfed autumnal larvae will die rather than spin 

 their cocoons although four or five months later they will spin their 

 cocoons but still require time to undergo the final changes and take the 

 needed time in the pupal stage. The experience of Studd and Moss 

 (posted) does not appear to support that of Robson as to early forcing 

 always resulting in an extended pupal period, and Baynes notes that 

 he collected autumnal larvae in i860, that they were subjected to 

 forcing treatment and spun up November 24th, the larvae emerging 

 between December 21st, i860, and January 6th, 1861. Studd 

 notes that the insect is easily forced at any time during the 

 winter, e.g., December — March, and he observes that emergences took 

 place on January 13th — February 4th, 1897, January 24th — March 6th, 

 1899. The larvae placed in heat (about 8o°F.), spin up in a few days 

 and emerge in from 10 days to a fortnight after pupation. Moss records 

 that he kept larvae in a cold frame in the winter of 1892 — 3, the grass 

 and moss were frozen in January, but the larvae were taken in- 

 doors — kept in a temperature of 8o°F., pupated within five days, 

 and in ten days more commenced to emerge. Buckler gives 

 (E.M.M., xi., p. 188) an excellent account of how to hybernate this 

 species successfully, viz., on the short turf of a lawn under a garden 

 hand-glass with a movable top, a frame being sunk into the ground 

 about three inches, and the larvae supplied with heather until they cease 

 to feed. The top glass was occasionally removed to promote ventila- 

 tion and to prevent mouldiness, and the larvae formed hibernacula 

 in little cavities hollowed out in the turf close to the roots of the grass. 

 The larvae came up on sunny days in spring, and between the 21st and 

 24th most of them disappeared beneath the grass and made their 

 cocoons, imagines appearing between April 29th and May 17th, 1873. 

 Hewett writes : " To winter M. rubi, plant a root of heather 

 out of doors, knock the bottom out of a small tub or box, put it 

 round the heather and cover it with perforated zinc. The larvae 

 may be under snow ; they will come up in March, and appear to 

 be pleased to have new shoots of heather to sit on and spin 

 among, but they eat nothing more." Holland noted that the larvae 

 being exceptionally abundant at Reading, in October, 1890, he 

 knocked the lid and bottom from a large box, nailed perforated 

 zinc over it, planted heather in the garden in a thick mass, 

 turned the caterpillars into the middle of it, placed the box over 

 and earthed up the bottom edge a bit. Nothing was done during the 

 winter but brush a heap of snow from the zinc once or twice ; in 

 spring the larvae came up in the sun to dry their coats, and soon spun 

 cocoons in the heather, coming through as moths well with very 



