176 THE ENTOMOLOGIST. 



to the var. polaris. Two years later W. von Keichenau* repeated 

 and enlarged these early experiments, when he, on the one 

 hand, let the larvae and pupae develop at a high summer tem- 

 perature under the influence of the direct rays of the sun, and, 

 on the other, reared them in the autumn at 5-12° C. The former 

 produced " beautiful fiery butterflies, which approached the var. 

 turcica''; the latter produced 'Wery dusky butterflies, notice- 

 ably brownish yellow with very large black spots." Dixey's 

 spots 6 and 7 especially are considerably diminished in the 

 heat form. 



It is not evident from these experiments whether the tem- 

 perature exercises its influence for alteration in the colouring at 

 any determined time of the development, since the heat or cold 

 — as, indeed, is advisable in early experiments— is acting during 

 the whole development. 



Dr. M. Standfuss, the experienced breeder of Lepidoptera, 

 has, however, recently published experiments with Vanessa 

 nrticcB. He placed the pupae for 60 hours in a temperature of 

 37° C, and noticed from this an approach to the var. ichnusa (or 

 turcica) make its appearance, although this form was never 

 quite reached. On the other hand, he placed pupae in a re- 

 frigerator for 32 days, and thus reared in a room, after 9 or 10 

 days more, dark specimens with large black spots and much blue 

 on the outer margin; likewise, therefore, an approach to the 

 polar form of urticce. 



These experiments confirm the results of Von Eeichenau in 

 general, and at the same time they show, that the action of 

 temperature falls wholly in the pupal period. 



E. Fischer also repeated experiments of this kind with 

 V. urticce, and partly reared the var. turcica from pupae, which 

 had been subjected to "a tolerably high stove temperature 

 (34-38° C.) for only a few days." (* Transmutation," &c. Ber- 

 lin, 1895.) 



The few experiments which I myself have conducted with 

 V. urticce, in general, indeed, confirm these results, but they do 

 not make so clear and striking an impression as do those of 

 Von Reichenau especially. In the latter's experiments all the 

 specimens appear to have been altered each time in the same 

 striking way. Unfortunately no details of them are given. It 

 is possible that this is attributable to the very high temperature 

 which Von Reichenau made use of — up to 45° C. in the sun. 



But E. Fischer also, who employed a temperature up to 

 38° C, only reared the var. turcica *' from a small portion of the 

 pupae," as I had done in my heat experiments, where 32*8 C. 

 was the highest employed. 



-■' W. von Keichenau, *• Die Zuchtungdes Nesselfalters {Vanessa urticm, 

 L.), ein Beweis flir den directen Einfluss des Klimas," in 'Kosmos,' v. 12, 

 1882, p. 46. 



