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XVI. Contributions to the Life History of Polyommatus eros. 

 By T. A. Chapman, M.D., F.Z.S. 



[Read October 7th, 1914.] 



Plates LXIX-LXXXIV. 



I HAD long had a wish to know something of the Hfe- 

 history of Polyommatus eros and to see its, so far, unknown 

 larva. The first practical step was, of course, to determine 

 its food-plant (or food-plants). No satisfactory oppor- 

 tunity to do this occurred to me until in July 1912, at Val 

 d'Isere, I found the species not uncommonly. It occurred 

 most freely where Oxytropis campestris grew, and I suc- 

 ceeded in observing a butterfly laying its eggs on this 

 plant. 



As I note later, I secured some eggs and got the larvae 

 into hibernation, but got none past the hibernating (third) 

 instar. 



At Le Lautaret, from the 21st July to the 5th August 

 1913, P. eros occurred practically everywhere. It was 

 certainly most abundant at two or three places where 

 Oxytropis caynpestris grew in quantity, and less so when 

 the Oxytropis was more scattered in growth. It was 

 also fairly common in places where Astragalus aristatus 

 flourished. Its more general distribution in smaller 

 numbers probably depended on Phaca astragalina, which 

 was not often abundant but grew almost everywhere. 

 The butterfly was seen to lay eggs on these plants, and the 

 larvae ate them readily. There was also a plant, Astragalus 

 onobryckis, which grew freely in one or two spots at Bourg 

 d'Oisans, much below the limits of P. eros, but the 

 leaves and seed pods of which seemed so very much like 

 those of 0. campestris, that I offered it to the larvae of 

 P. eros and they ate it as readily as the Oxytropis. With 

 these four plants nearly equally acceptable to the larvae, 

 it is very unlikely that there are not other allied plants 

 that they would also readily eat. The butterflies were 

 seen at various elevations. Nearly as low as 5000 feet 

 towards Monetier where the food-plant was probably 

 the Astragalus aristatus, and up to 7500 feet where Oxy- 

 tropis campestris was abundant. They probably occurred 



TRANS. ENT. SOC. LOND. 1914. — PARTS III, IV. (fEB.) 



