156 BRITISH BUTTERFLIES. 



differentiated ; this is by no means improbable. On the other hand, when we note 

 how many pairs of blues there are that resemble one another extremely, and yet 

 are comparatively unrelated [Cupido minimus (and still more its congener C. sebrus) 

 and Cyaniris semiargus are the best examples British species afford], we cannot 

 help speculating whether this be not another instance. In other words, were 

 argyrognomon and aegon one species which divided into two, acquiring hardly any 

 general characters to distinguish them, but becoming very different in the ancillary 

 organs ? Or were they two very different species (in facies) derived from different 

 points of the Plebeiid tribe, that were forced to acquire a very similar facies ? In 

 the former case they form one genus, in the latter they do not. Since there is no 

 strong argument to be advanced on either side, it seems proper to leave the present 

 belief in their close relationship undisturbed, and let them remain together, and 

 note any details in support of it. P. argus (aegon) is characterised by the length 

 and slenderness of both the dorsal process and the upright portion of the hook. 

 The dorsal process is also curved in such a way that, when the parts are flattened, 

 as occurs when mounting them on a slide, the dorsal armature has the closest 

 resemblance to the harp-like tail of the lyre-bird, or perhaps one ought to say to 

 the conventional harp that that tail so closely imitates. The end of the clasp in 

 argus {aegon), has, where other species have fine serrations along the spiracular 

 branch, very large and coarse spines, such as few other, and no British, 

 Plebeiid has. In view of the contention that argus (aegon) and argyrognomon 

 have but recently separated, it is well to note that this armature of 

 spines is very variable. The spines may be four, five, or six in 

 number, and there may or may not be present at either end of the series, small 

 teeth, minute in comparison with the great spines, but large in comparison 

 with the fine teeth usual in Plebeiids. When we come to argyrognomon, 

 we find the serrated edge of the spiracular branch of the spine is not orientated 

 obliquely or towards the middle line of the clasp, but is transverse, again unlike 

 other Plebeiids, whilst the teeth are distinctly larger than usual, and again show 

 considerable variation in size, always, however, ranging in order of size with other 

 Plebeiids, rather than with argus (aegon). P. lyaidas agrees fairly with argus 

 (aegon) in the dorsal armature, but is almost as near to Polyommatus iearus as to 

 this group in the serrations on the clasp. These are very fine, the alliance to 

 Plebeius argyrognomon is to be found in the fact that the serrated margin is terminal 

 and somewhat rounded, so that the end of the margin looks outwards from the middle 

 line of the clasp. 



Aricia : After Plebeius, this seems to be the most separable and distinct 

 section (with British representatives) of the tribe. It may be defined as the group 

 whose larvae feed on Geraniaceae, and includes astrarche, idas, donzelii, and 

 eumedon. Taking A. astrarche as typical, we find it has a comparatively very 

 small hook to the dorsal process, and possesses, on the body of the clasp, in a longi- 

 tudinal line, a number of rough spinous processes. The other three species 

 illustrate both the strength of the ancillary appendages as proving relationships, 

 and the weakness inherent in reliance on one character. The appendages 

 are, however, a whole group of characters. We find idas and donzelii are almost 

 identical with astrarche in the smallness of the hook of the dorsal process. But 

 stimulating the imagination as much as may be by strenuously regarding astrarche, 

 fails to enable me to see any rough processes on the clasps of these two species. 

 They are present, however, in eumedon, but here we find the dorsal armature some- 

 what different, and the hook by no means a small one, still less minute. 



In dividing up the remainder of the species, it is less easy to give 

 crisp characters, as there is much variability within very narrow 

 limits. 



Vacciniina : As exemplified in optilete i 'f the ancillary appendages agree with 

 Aricia in having the serrate process of the clasp much larger than the soft one. It 

 disagrees with Aricia in that the dorsal -process is shorter and broader, and there- 

 fore more triangular. 



Cyaniims : As exemplified by semiargus and persephatta, this group agrees 

 also with Aricia in having the hard process markedly Larger than the soft one. but 



I" V. ojitilete is geuitalically a very typical Plebeiid, much nearer to icavis 

 than the appearance of the insect would lead one to suspect. T.A.C 



