EUTRICHID.E. 1 1 7 



larvae in two-thirds or less of the normal time*, and then emerged as 

 perfect insects in the same year, i.e., without hybernation of the larva 

 — of O. pruni ioo per cent., and of D. pini 8i per cent. The 

 larvae and pupae were kept as far as possible at a mean 

 temperature of 2 5°C. (77°F.). Part of the eggs laid by the same 

 females as those used in the above experiment, which had already 

 been laid in a temperature of about 2 2°C, and were kept in this 

 until hatched, afterwards remaining as larvae and pupae in the 

 same mean temperature of 2 5°C. as the first portion of the broods, 

 produced a considerably smaller number of perfect insects without 

 hybernation of the larvae, viz., O. pruni, 64 per cent., D. pini, 28 

 per cent. Standfuss concluded that the acceleration of development 

 which the larva had already undergone in the egg had transferred 

 the energy to the later stages of growth, and he pointed out that 

 the shortening of the period of development is, in very many 

 cases, associated with an obviously altered aspect of the imagines, 

 e.g., Eutricha populifolia compared with its var. aestiva (pbscura, Heu.), 

 and Odonestis pruni with its var. prunoides, and suggests that this 

 alteration in the aspect of the imagines of the late broods must 

 be influenced by the temperature to which these individuals have 

 been exposed in the egg stage. He has further dealt somewhat 

 at length with the differences presented by the two broods, where, 

 as is frequently the case, in a more or less complete manner and under 

 more or less favourable conditions, the species is completely or 

 partially double-brooded. There can be no doubt that a study 

 of the phenomena presented by complete and partial double- 

 broodedness would give important clues to the geographical 

 origin, and the phylogenetic age, of different forms of various species. 

 Standfuss, referring (Ent., xxvii., p. 73) to the difference between 

 Eutricha populifolia and its var. aestiva (=obscura, Heu.), and Odonestis 

 pruni and its var. prunoides, asks : " Are the two differently-formed 

 broods in instances like this of different phylogenetic age ? Eutricha 

 populifolia is probably of northern origin, although in the north 

 the species never produces two broods, whilst in the more 

 southerly parts of its distribution — Carinthia, Piedmont, and 

 south-east France — it often, possibly regularly, has a second 

 brood. Thus, E. populifolia would be the type and the second 

 generation, aestiva, the variety." As to the differences observable in 

 colour and size, in these seasonally dimorphic (or trimorphic) 

 Eutrichids, Standfuss asserts that such usually result in being 

 larger and more strongly pigmented when developed in late spring 

 and early summer, and smaller and more weakly pigmented in late 

 summer or autumn. He notes (Entom., xxviii., pp. 73-74) that a 

 pair of Eutricha quercifolia, of which the male measured 58mm. 

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

 which, on being reared at a temperature of 2 5°C. — 3o°C, and 

 after a sojourn of 70-85 days in the larval and 12-15 days 



* Belling records (Bert. Ent. Zeits.. xlv., Sitz. p 43) that a Berlin collector, 

 by keeping the insects in an uniform, moist and warm temperature, has reared three 

 generations of E. populifolia in a year, the second generation, from egg to imago 

 occupying only 25 days. The 2nd brood is known as var. obscura, Heu., the 3rd 

 brood as var. autumnalis, Jaen. Petersdorff also notes (loc. cit., p. 52) the rearing 

 of three broods of E. populifolia and two of E. qturci folia in one year. See also 

 Ent. Rec, xii., p. 1 1. 



