NOTES ON THE LIFE-HISTORY OF COLIAS NASTES. 125 



decreased further in size, but by December 25th, when my next 

 inspection took place, it was dead. 



The only other larva that reached the hybernating stage was 

 similar in all respects to the one above described, except that it 

 was entirely devoid of the light yellow subdorsal stripes ; in 

 place of these in all stages it had the dark subdorsal lines that 

 characterized the third instar of the first larva. 



From the above observations it appears evident that the 

 larva of this species hybernates as a full-fed larva. Assuming 

 that it must hybernate as a larva at all — and all the Colias 

 species I am acquainted with do pass the winter in this stage — 

 then the reason is evident, for the whole of its habitat is covered 

 with snow several feet deep from September until May, and the 

 winter frosts are so intense that every herbaceous plant is cut 

 down and killed to the ground ; therefore, on the snow melting 

 in the spring, there would be nothing for the larva to feed 

 upon. 



It has been stated in a German magazine that the food-plant 

 of Colias var. loerdandi is Oxytropis lapponica. This is certainly 

 an error, for two extremely competent Swedish botanists who 

 were at Abisko in July last not only identified it as Astragalus 

 alpinus, but informed me that 0. lapponica is not found in 

 Swedish Lapland, nor is it mentioned in the * Flora Lapponica ' 

 of Linne. A. alpinus is an exceedingly abundant plant at 

 Abisko, and is the only leguminous plant I saw there. 



It must be borne in mind that the Province of Tornea Lapp- 

 mark, which appears to be the chief habitat of Colias var. 

 icerdandi, is practically without cultivation, anything in the 

 nature of a meadow being unknown, except perhaps in the 

 vicinity of the few small towns or villages, everything elsewhere 

 being entirely mountain, moor, swamp, or forest, and from all 

 these the leguminous plants of cultivation are entirely absent. 

 In the * Flora Lapponica ' of Linne only nine species of this 

 order are mentioned. 



The above observations on the life-history of this species 

 throw some light on a problem on which there has been con- 

 siderable spe3ulation amongst lepidopterists, i. e. how do the 

 larvae find time to complete all their stages during the very short 

 Arctic summer ? It has been suggested as a way out of the 

 difficulty that many, if not all, of them may feed for two seasons. 

 My observations on Colias var. werdandi seem to show, however, 

 that some, if not the bulk, of the species feed rapidly whilst they 

 have a chance, and pass the winter as full-fed larvae or as 

 pupae. I hope, however, to throw further light on this question 

 at a future date. 



Youlgreave, South Croydon : February 10th, 1912. 



BNTOM. — APRIL, 1912. L 



