154 THE ENTOMOLOGIST. 



the room until the first moult. This took place on May 5th and 

 the following days at a temperature of only 10° C. As soon as 

 the weather became warmer, the larva-cage, in which the young 

 larvae were now being reared on living grass with free access of 

 air, was brought into a well-lighted but cool cellar, where 

 the temperature was always 12'5-14° C. Strictly speaking, the 

 rearing might have been carried on at the actually prevailing 

 heat of 25-27° C, to which, indeed^ our indigenous egeria are 

 subjected ; but the other method was chosen, in order to obtain 

 as distinct a result as possible. 



The larvae grew very slowly ; they were only 12-13 mm. long 

 on May 28th, and their pupation took place between June 17th 

 and 25th. They produced 15 pupae, which were left in the 

 cellar at a maximum temperature of 14° C. Shortly before 

 emergence the temperature rose somewhat, but only up to 

 17-19° C, consequently far from our highest summer tempera- 

 ture. There emerged : — 



On 



July 



12th, 



1 butterfly. 





J) 



13th, 



5 butterflies. 





)) 



14th, 



5 „ 





5? 



15th, 



2 „ 





>) 



17th, 



3 



Altogether If) butterflies : 



'O 



8 of them males and 8 females, all smaller and less brightly 

 yellow than those which had been captured at Genoa in March 

 and April, but all at the same time distinctly more brownish 

 in the ground colour and yellower in the spots than specimens 

 captured at Freiburg or elsewhere in Germany. There is no 

 doubt but that a brood of egeria from Germany would have pro- 

 duced paler butterflies, if they had grown up under closely 

 similar conditions. But the force of this argument is still 

 stronger from the following experiment. 



Second experiment with egeria. — From 20 eggs of an egeria 

 from Ziirich, which were laid on May 20th, 1886, there emerged 

 20 larvae at 19° C. on May 30th, which on May 31st were 

 placed on living grass in a hot incubator at 25-27° C. On this 

 account the larvae were very active ; they ate much and grew 

 rapidly, so that they had all got over the first moult as early as 

 June 1st. The temperature was not always quite constant, but 

 sank on June 5th to 24° C, then rose again on June 7th and 8th 

 to 25° C, and remained so. On June 9th the larvae measured 

 1*5 cm. ; on June 13th the largest was 1*8 cm. I found three 

 pupated on the 18th, three more on the 21st, one more on the 

 24th, and the last on the 25th. On June 5th, on changing the 

 grass, as it had to be done from time to time, three larvae 

 remained unnoticed on the old plant, which was placed in the 



