SEASONAL DIMORPHISM OF LEPIDOPTEBA. 175 



Third experiment with urticce. — As an opposite experiment 

 to the preceding, a part of the larvae of the second experiment 

 were reared in a cellar at 15° C. Pupation first began on 

 August 7th, and the butterflies emerged between August 27th 

 and 29th. 



The 10 specimens reared in this way are a little darker than 

 those of the second experiment ; the outer margin is somewhat 

 blacker, and, before all, the spots are larger, especially spots 5 

 and 6, at least, in nine specimens. They are, however, still far 

 from the var. polaris. 



Fourth experiment with urticce.—K nest of recently-hatched 

 larvae, found near Freiburg on Aug. 31st, was reared at a room 

 temperature of 17-23° C. ; after Sept. 16th it was only 17-20° C 

 Pupation took place between Sept. 25th and 28th. 



The 22 butterflies reared are all rather bright, with small 

 spots ; in seven specimens the spot 6 is quite small, and in one of 

 them only a suggeUion ; the outer margin is less dark than in the 

 second and third experiments; and in no specimens are the spots 

 so large as in these experiments. 



The experiment, at all events, proves that the spots 7 

 and 6 can also turn out quite small at a medium tempera- 

 ture independently of heat. Hereditary predisposition there- 

 fore co-operates here also with individual differences, and 

 consequently it cannot be said, in a particular case, how much 

 is to be attributed to the one and how much to the other 

 factor. 



Fifth experiment ivith urticce, 1888. — A nest of recently- 

 hatched larvae, found in the level country near Freiburg on 

 Aug. 4th, was reared in the incubator at a temperature for the 

 most part of 30° C. ; fluctuations, however, occurred between a 

 minimum of 25° C. and a maximum of 32-8° C. Pupation began 

 as soon as Aug. 13th, and 8 butterflies emerged by the 18th, 

 followed by 24 more on the 19th, 1 on the 20th, and 2 more on 

 the 21st. 



None of these 35 butterflies were especially dark ; on the 

 contrary, all were brilliantly red in the ground colour, and with 

 relatively little black ; the outer margin forms, towards the 

 inside, a narrow regularly dentate black stripe, and the spots 6, 

 7, and 8 are of the usual medium size in only one specimen ; in 

 all the rest they are small up to the point of complete dis- 

 appearance. Spot 6 is completely wanting in one specimen, 

 while 7 is faint ; in another 6 is faint, and 7 more distinct ; 

 these spots are unusually small with the majority. This marking 

 closely approaches the Corsican variety ichnusa. 



Results of the experiments ivith urticcB. — Experiments similar 

 to those here described have been repeatedly carried out before. 

 In 1880, by means of a somewhat diminished temperature, 

 Dorfmeister obtained a powdering of the butterflies, transitions 



