RUMICIA PHLJ3AS. 



333 



31st. On September 12th, they were placed in an " incubator," the 

 temperature kept at about 27°-29°C, pupation taking place therein 

 between September 15th-24th — 25 pupae in all, which produced 23 

 butterflies between September 19th and October 5th, the remaining 

 pupae not emerging. The temperature of the incubator was gradually 

 raised from 24°C. on September 25th, to 3S°C. on September 29th. 

 The imagines divided as follows: 



a. Eight specimens closely resembled the ordinary German G. phlaeas, so that 

 the raised temperature had no effect on them. 



/3. Two specimens can be described as var. eleus, as they are as strongly powdered 

 with black as many specimens of the darkest variety of the butterfly reared at 

 Naples. Both specimens emerged on September 27th, i.e., two days before the 

 end of the period of emergence, and, consequently, were not subjected to the highest 

 temperature, 37°C.-38°C., but only to a temperature of 23°C.-29°C. 



y. Thirteen specimens are somewhat darker that the ordinary German form. 

 They have the black margin a little broader, the black spots somewhat larger. The 

 black powdering of eleus is also present to a very slight extent, and principally on 

 the lower half of forewing, from base towards the band of spots only. A sharp 

 distinction cannot be drawn between these and the unaltered ones first mentioned. 



As a summary of the results, it will be noted that the eggs of 

 Neapolitan butterflies more frequently produced butterflies powdered 

 with black at Naples than when reared at Freiburg in a room at ordinary 

 summer temperature, and resulted in butterflies without any black 

 powdering when the pupa were kept at 6°C.-10°C. ; on the other hand, 

 eggs from north German phlaeas produced two specimens powdered 

 with black, similar to Neapolitan eleus, when the pupae were subjected 

 to 24°C.-38°C. Weismann considers that experiment 2 (supra) proves 

 that temperature only operates during the pupal period, its operation 

 during the larval period being without effect, since the Neapolitan 

 larvae, all reared at the same room-temperature, and only treated 

 differently during and after pupation, produced strikingly different 

 coloration in lots a and p. He thinks that there can be little 

 doubt that there is a greater tendency towards black colouring in 

 the southern summer broods, although the spring brood in the south is 

 as pure red-gold as in central Europe, etc. Merrifield's experiments 

 (Trans. Ent. Soc. Lond., 1893, pp. 63 et seq.) tend to show that the 

 difference in appearance, between the phlaeas from southern Europe and 

 England, is not necessarily to be attributed to the existence of races of 

 different colouring, but may be due to the difference between the 

 temperatures to which the individuals are exposed in the two climates. 

 Starting with eggs laid by English phlaeas, he obtained 70 pupae, and 

 forcing (or retarding) them at different temperatures, obtained results 

 as follows : 



a. Ten pupae. Forced at 80°F.-90°F. (representing a very hot continental 

 summer temperature) (figs. 1 and la). Emerged in six days. Spots large, not 

 sharply defined ; dusky suffusion of forewings. 



/3. Six pupae. Temperature of room, about 70°F. (English summer tempera- 

 ture). Emerged in 11-15 days. Spots smaller ; copper colour more vivid ; black 

 more intense. 



y. Six pupas. Placed in a cool shady place out-of-doors, 56°F.-58 F. (rather 

 cool summer or late spring temperature). Emerged in 22-23 days. Copper colour 

 still more vivid ; copper band on hindwings broader. 



S. Ten pupae. Placed in a cellar at uniform temperature of about 56°F. 

 Emerged in 29-33 days. These are very similar to last lot. 



e. Six pupae. Placed in refrigerator at about 47°F. (temperature of cold spring). 

 Only three emerged, and these took 57-59 days to develop. Effects noted in y and 

 $ intensified. 



