542 



BRITISH LEPIDOPTEEA. 



What conditions led to the specialisation of the genitalia of rubwundm 

 in a certain direction, so that they became constantly different from 

 those of the stem form ? 



We may now consider A. viciae, better known under its synonym 

 of meliloti. The distribution of this species is remarkable, extending 

 from Barbary to Scandinavia, and from the New Forest (its most 

 western limit), throughout Europe and Asia to Dahuria and Amurland. 

 It is local, occurring generally in great abundance in limited districts, 

 of which our New Forest locality may be considered an almost typical 

 one. It haunts borders of woods and wood-clearings, but what limits 

 it to these districts has yet to be discovered, nor can we suggest a cause. 

 Are the reputed food-plants not the natural ones ? Is it confined to a 

 special species of plant that extends locally over all its range ? We 

 do not know, yet it should not be difficult to discover. Over such an 

 area the conditions of environment must be extremely varied, yet 

 under somewhat similar conditions the same form (the one we know 

 so well) is maintained, the specimens from Germany, France, the 

 Baltic provinces and Asia Minor, being almost identical with our 

 British examples. By the time the insect has reached its most 

 northern and western limits, some degree of variation is noticed ; the 

 thin scaling is maintained, the general facies is little altered, but the 

 hind-wings show an increase in the width of the marginal border, and 

 the red colour is reduced to a minimum. These appear to be the only 

 essential differences, yet they have a marked effect on the general 

 appearance of the insect. In Finland this race is known as ehnbeiyii, 

 in Amurland as dahurica. An occasional British specimen will show 

 a few red scales on the abdomen, a suggestion of an abdominal ring in 

 embryo. In Pomerania and the Baltic provinces similar examples are 

 found, whilst an occasional specimen will have the ring almost com- 

 plete, forming the ab. stentzii. In Boumania, where the insect is 

 very abundant, a strange development occurs, for typical viciae are 

 here mixed with individuals which Caradja is unable to separate from 

 dahurica, whilst the red-ringed form is by no means rare. Occasionally, 

 in Britain, and in the localities of north and central Europe, an 

 example is found with the spots 1, 2 -f 4,3 + 5, forming three wedge- 

 shaped streaks, as in A. purpuralis, but the aberration is exceedingly 

 rare. In the Ala Tau district this is the common form, and Staudinger 

 has termed the local race confusa. So far, however, these local races 

 differ but little radically, and in general appearance, from the type. In 

 the warm, southern, transalpine valleys, however, a change occurs. 

 A. viciae, as we know it, appears to be almost unknown, but in its 

 place we have an insect thickly scaled with brighter red markings, 

 with a very characteristically marked marginal border to the hind- 

 wings, and with a tendency to develop a strongly marked and brightly 

 coloured red abdominal belt. In addition, this form has spot 6 

 developed, not strongly in all specimens, but as well-developed, say, as 

 is the corresponding spot in the south-alpine forms of A. oehsenlieimeri. 

 This insect is the charon of Hiibner, and even on superficial grounds 

 one feels inclined to say at once that it is a distinct species. Calberla, 

 however, has come to a different conclusion, and considers it simply a 

 transalpine form of A. viciae, although at present he has published no 

 critical comparative life-histories of the two insects, which alone can 

 determine the matter. It might be supposed that the presence of the 



