VARIATION AND ABEERATION IN BUTTERFLIES. 73 



pp. 81, 82) that with the shortening of the period of development 

 is associated in very many cases an obviously altered aspect of 

 the perfect insect, affecting both size, form, and colouring, as in 

 Lasiocampa populifolia, Esp., compared with var. cestiva, Stgr., 

 and L. pruni, L., with var. prunoides, Beck. 



According to the experiments now recorded it would seem 

 that this alteration in aspect of the perfect insect, to judge at 

 least by the number of individuals that show it, must be in- 

 fluenced by the temperature to which these individuals have 

 been exposed in the egg-stage ; so that, if any one wishes to rear 

 such specimens, he must, if possible, keep even the egg at a 

 raised temperature. A series of interesting observations might 

 undoubtedly be made by taking the opposite course, by lowering 

 the temperature, that is to say, and so keeping back the eggs. 

 Many years ago I made an experiment of this kind with a large 

 number of eggs of the second brood of L. priuii, unfortunately 

 without result, owing to inexperience and lack of sufficient care. 

 With greater attention this experiment might very easily be 

 carried to a successful issue.* 



II. The Larva. 



The only experiments conducted by me with reference to the 

 possible dependence of divergences in the perfect form on larval 

 conditions have been on the mfluence of temperature, food, and 

 light. In this case also, as regards the first of the three factors, 

 viz., temperature, the experiments consisted entirely in raising 

 it to a height of 25—30° C. (77—86° F.). 



(1) Size. — The regular, almost invariable, effect was as 

 follows : the more the period of larval feeding was shortened by 

 the raising of the temperature, the better marked was the 

 reduction in size of the imago. 



A pair of L. quercifolia, of which the male measured 58 and 

 the female 89 millim. across the wings, produced offspring of 

 which, after a sojourn of 70—85 days in the larval, and 12 — 15 

 days in the pupal condition, the males measured only 35 — 37 

 and the females 36 — 39 millim. across the wings. A. fasciata 

 (male 46, female 48 millim. across) from pupee collected in the 

 open air, produced three females measuring 36 — 39 millim. after 

 a larval stage of 68 — 87 and a pupal of 15 — 20 days. Calli- 

 morpha dominula, L., var. romanovi, Stgr. <? (59 millim.), and 

 var. persona, Hb. ? (55 millim.), gave rise, after 65 — 71 days of 

 larval feeding and 14 — 19 days in the pupal stage, to a form 



* Extensive experiments with reference to the influence of temperature 

 — including a very abrupt change of temperature — on the development of 

 the egg of Bomhyx mori, L., will be found in the Eeports of the Caucasian 

 Bilkworm-rearmg Station at Tiiiis (a Government institution) for the year 

 1891. Unfortunately they are in Russian. 



