PLUSIA FESTUC^ AND ITS SECOND BEOOD. 113 



Jaly, but yet in some specimens with a slight approach to 

 porima. At all events, a high temperature itself has, as a rule, 

 very little effect on pupae of the third brood, which have once 

 been exposed to it for some weeks without developing. They all 

 produce the levana-form, although frequently tending somewhat 

 towards porima ; in this way the 34 butterflies of Experiment 1 

 emerged, which were forced by heat as soon as the end of 

 January. 



Viewed apart from any theory, the facts, shortly put together, 

 are the foil -wing : levana d,ndi prorsa follow one another in the 

 open with us in a regular cycle in such a way that, as has been 

 known for a long time, levana occurs in April, prorsa in June. 

 By the influence of cold immediately after pupation the second 

 brood may be induced to assume more or less the form of the 

 first, i.e. the levana-iovm ; but the tendency to the prorsa-fonn. 

 is stronger in this brood, and it does not succeed in making 

 every individual levana. On the other hand, the third brood has, 

 in the greater number of individuals, a strong tendency towards 

 hybernation and to the levana-iorm. But there are single in- 

 dividuals, which form prorsa at once without the influence of a 

 higher temperature, and the majority of the rest can be induced 

 to become more or less pure prorsa by the influence of a high 

 temperature on the fresh pupse. Intermediate forms, so called 

 porima, arise, wherever a brood is affected by an unsuitable 

 temperature at the beginning of its pupal period ; thus with the 

 second brood by unusual cold, with the third by unusual heat. 



I shall speak of the theoretic significance of these facts in the 

 general part. 



(To be continued.) 



PLUSIA FESTUCjE and ITS SECOND BROOD. 

 By J. Arkle. 



On a hot sunny afternoon. May 6th, 1893, whilst watching a 

 number of dragonflies {Ischnura elegans) flying about or resting 

 upon the sedge Glyceria aquatica, my attention was arrested by 

 a small hammock of white silk slung up near the bent top of a 

 sedge leaf. I had never seen such a thing before, but I felt sure 

 it was a cocoon of P. festucce. And so it was. The dragonflies 

 were left to themselves, and at the end of a close search I had 

 taken six pupae. The moths all emerged between June 5th 

 and 10th. 



Although I kept a sharp look on the place, I saw no further 

 trace of the insect until Aug. 3rd, when I found seven pupae spun 

 up about twenty yards from where I took the first. Three moths 

 emerged on the 7th, two on the 16th, and another on the 18th. 



ENTOM. — APRIL, 1896. K 



