Seasonal dimorphism of lepidoptera. lo^ 



apples covered with treacle — failed absolutely ; inferior, also, 

 were the results of my own method — putting the treacle on the 

 leaves of trees; true, the moths were attracted by it in great 

 numbers ; but if in taking the first the leaf was set swinging, the 

 others were sure to fly away or fall down before attention could 

 be given to them. 



Taking into account the above, it is possible to foretell in 

 some measure the chances of success or failure on a given 

 evening, which in some cases it is important to know before- 

 hand. 



St. Petersburg University, Jan. 15th, 1896. 



NEW EXPERIMENTS ON THE SEASONAL DIMORPHISM 

 OF LEPIDOPTERA. 



By Dr. August Weismann. 



(Translated from the German by W. E. Nicholson, F.E.S.) 



(Continued from p. 80.) 



Third experiment with bryonies. — On June 19th, 1888, I 

 again received captured females of hryonice, despatched by the 

 kindness of Pastor Hauri at Davos, 22 of which arrived alive. 

 From June 25th onwards they laid eggs on rape, and the larvae 

 emerged between June 2r)th and July 1st. They were reared on 

 plants kept in water in a room at 17-23° C, and were divided 

 into two lots on July 25th. 



Lot I., distinguished as Experiment III. a, was left until 

 pupation took place in the breeding-cage at the summer room 

 temperature (always very warm). Pupation took place between 

 July 20th and 28th. Although the room temperature in August 

 was still about 20° C, yet no specimen emerged ; all the pupae 

 were hybernated in a warm room, and produced nine completely 

 normal butterflies in the spring of 1888, 3 males and 6 females, 

 viz. 1 male on March 23rd and April 15th and 18th, and 1 female 

 on April 29th and May 25th, and 2 females on May 27th. 



Lot IL, distinguished as Experiment III. Z^, was taken, on 

 July 25th, 1888, from the room temperature at 23*8° C. into the 

 incubator at 30° C, and remained there until Aug. 19th. Pupa- 

 tion took place about the same time as with lot I., namely, 

 between July 20th and 28th. Although the temperature of the 

 incubator never sank below 25° C, and was generally at 29° C, 

 frequently also 31°, and once 32*8° C, yet no specimen emerged. 

 From Aug. 19th onwards the pupae were again kept in the room 

 temperature, and during the winter in a cold room. 



The emergence of 32 butterflies, 23 male^ and 9 females, first 

 took place in the spring of 1889, viz. : — 



