ANTHEOCERID SPECIES. 543 



6th spot would settle the specific distinction of charon, but Fletcher, 

 Christy, and others, possess British specimens of A. viciae with spot 

 6 more or less well-developed. If charon be really a transalpine race 

 of A. viciae, then the climatic conditions, and the more nutritious food 

 of the southern countries, are possibly the factors that have determined 

 the great superficial differences that exist between our A. viciae and 

 the charon dwelling beyond the Alps. 



A. lonicerae is the most constant, A. trifolii the most variable, of all 

 our British species, the former probably the most constant in the character 

 of its environment, the latter the most variable. Bateson is unable 

 to separate A. lonicerae and A. trifolii by their genitalia, yet one can 

 determine the larvse and imagines readily enough, and the similarity of 

 the genital organs is emphasised by the fact that the two species 

 hybridise freely inter se, and produce fertile progeny. Here, then, the 

 specific difference is not due to a specialisation of the genital organs, 

 but must be due to isolation in some other form. To a certain extent 

 isolation may be brought about by a difference in time of appearance, 

 for A. lonicerae is decidedly later than A. trifolii in the normal time of 

 its appearance, and earlier than A. palustris. The specialisation to a 

 certain food-plant may be potent, although as yet insufficient attention 

 has been paid thereto, and it is quite possible that A. palustris is 

 specialised from A. trifolii by being limited to Lotus uliginosus. Both 

 A. lonicerae and A. trifolii present many interesting phases in the 

 question of species on the continent, the former in its relation to A. 

 medicaginis, the latter in its relation to A. palustris and the extreme 

 form of the latter, A seriziati. A. trifolii presents us, as we have 

 already seen, with two distinct races in Britain, A. trifolii and A. 

 palustris, already dealt with at length, distinct enough in their 

 extremes, and clearly responding to their environment. The small 

 meadow and hillside form prefers a dry habitat, appears in June 

 (sometimes in May), which suggests that the nature of the habitat 

 governs, to some extent, the time of its appearance. It has a less 

 succulent food-plant (Lotus corniculatus), and probably as a result it is 

 of smaller size, rather less brilliant tint, and has generally a wider 

 marginal band to the hind-wings. The larger marsh form prefers a 

 moist habitat, and appears in July and August, it has a more succulent 

 food-plant (Lotus ulujinosus), is of larger size, more brilliant tint, 

 rather narrower marginal band to hind-wings, etc. In their extremes, 

 therefore, the insects are distinct enough, and the nature of their 

 respective habitats with the resulting isolation as to time of appearance 

 engendered thereby, appear to be sufficient to bring about a very 

 definite separation. Intermediate conditions possibly do prevail, and 

 the extremes appear to be united by overlapping forms, so that it is 

 difficult to consider them as species. Here, then, is a distinct factor 

 that weighs in the determination of species, viz., the positive separation 

 of distinct forms or races (by their environment, etc.), e.g., lonicerae 

 and trifolii, the union of otherwise distinct races (with a different 

 environment) by intermediate forms (with an intermediate environ- 

 ment). Yet the strongly-marked larva of A. trifolii is as different in 

 appearance as possible when compared with the pale, scantily-marked 

 larva of A. palustris. We are not prepared to enter into the effect of 

 the wider geographical conditions to which A. trifolii is subjected, for, 

 with the exception of the French lepidopterists, it is doubtful whether 



