AGRIADES. 323 



single-brooded species, and, whilst A. thetis hybernates in the normal 

 fashion of the Plebeiid larva in its third instar, A. coridon hybernates 

 as an unhatched larva inside the eggshell. It is probably in this 

 physiological peculiarity that we have to seek for one of the causes of 

 the maintainance of two such closely allied species, with an almost 

 identical limitation of range, and largely confined to the same 

 foodplant. 



The Agriadid pupa (as represented by those of Agriades thetis and 

 A. coridon) is rather less broad and short proportionally than the 

 Cyanirid pupa (as illustrated by that of Cyaniris semiargus). It is 

 also denser, thicker, and more coloured than that of Cyaniris. The 

 pupa-skin of C. semiargus is of a very delicate texture, thin and trans- 

 parent (almost filmy), whilst those of Agriades thetis and A. coridon 

 are comparatively dense, the skin (apart from the appendages, wings, 

 etc.) quite brown-tinted in A. thetis, though less coloured in that of A. 

 coridon. The abdominal pocket situated between the 4th and 5th 

 abdominal segments, for the end of the maxillae, and noted antea p. 

 226, as specially well-developed in Plebeins, and comparatively rudimen- 

 tary in Cyaniris (semiargus) (p. 252), is fairly well developed in Agriades 

 (thetis and coridon). The Agriadid pupa (thetis and coridon) is without 

 definite cremaster, and has no cremastral hooks, although the 

 cremastral area carries some ordinary hairs, which are not, however, 

 homologous with the cremastral hooks ; the Cyanirid pupa (semiargus) 

 has a cremaster of quite normal structure, although the hooks are very 

 sparsely developed. Both the Agriadid and Cyanirid pupge are 

 essentially naked, but the former has quite a number of hairs round 

 the spiracles to compare with the one or two of the latter (Chapman). 



The range of the two species included in this genus is very limited, 

 being confined in each case to central and southern Europe. They 

 both extend to the Asia Minor and Caspian districts, but not beyond 

 Persia, nor do they apparently enter Asia beyond the Urals. A. thetis 

 (bellargus) extends into Mauretania, but A. coridon has not yet been 

 reported as occurring on the southern shores of the Mediterranean. It 

 is also a remarkable fact that, in its most western limits, A. coridon, in 

 the so-called form polonus, Zell. (but really the form polona, Gerhard), 

 is so like A. thetis (bellargus) in certain superficial characters of colour, 

 etc., that Staudinger treats it (Cat., 3rd ed., p. 86) as a var. of bellargus, 

 and then notes it as " corydon var. caucasicae valde similis." It is 

 very rarely that two so closely allied species show such a near 

 parallelism in their range and habits. The question of hybridity 

 between the two common Agriadid species has already been broached. 

 On May 20th, 1893, we captured at Cuxton a $ example of a " blue " 

 that, in shape, size, and general appearance, might be coridon, but 

 which, in colour, approaches thetis (bellargus). It was at the time paired 

 with an ordinary $ thetis (bellargus) (which it carried when they were 

 disturbed), and was flying among hundreds of quite typical thetis 

 (bellargus), no specimen of coridon being seen, nor, indeed, did 

 coridon appear in this locality that year till a month later. As 

 late examples of coridon and the early examples of thetis (bellargus) 

 frequently occur together at the end of August and early September 

 in this locality, we concluded that the specimen was a hybrid between 

 these species, retaining the form, size, etc., of coridon, but having 

 the scales and colour modified in the direction of thetis (bellargus). 



