10 THB ENTOMOLOGIST. 



because in other places neighbouring valleys produce such dis- 

 tinctive forms that one would require a detailed knowledge of 

 all localities to cope with them ; and thirdly, because no sooner 

 does one seem to have discovered a rule than it is upset by the 

 next piece of knowledge acquired on the subject. As an example 

 of the first difficulty 1 may refer to the specimens bred by Mr. 

 South from North Devon larvae, which were exhibited at the 

 South London Society, and of which an account may be seen in 

 the * Proceedings ' of that Society for 1885, p. 33 ; with them 

 were exhibited specimens of Swiss aurelia, parthenie, and didynna 

 to show how these English specimens approached in different 

 instances one or other of these forms. These specimens having 

 been long dispersed I have been unable to see them, but the 

 facts adduced, together with Kane's comments on them (Entom. 

 xix. p. 145, 1886), are a striking example of the difficulty referred 

 to. With regard to the differences between neighbouring localities 

 I may mention the forms found in the valley of the Aven9on 

 behind Bex, and in the little valley behind Lavey-les-Bains, the 

 very next opening from the Ehone Valley, and on the same side 

 of it; the specimens from the iirst locality being large and 

 bright, and the black markings of fairly even breadth, those 

 from the other being small, of a rather pale ground colour, and 

 the black markings having a tendency to form broadish central 

 and narrow outer lines. This may be accounted for by the fact 

 that the valley of the Avencon is moist and the other dry, so that 

 the food-plant in the former is juicier and more nutritive than 

 in the latter. With regard to the third difficulty, I may adduce 

 the observation of Kiihl and other Swiss authors to the effect that 

 in Tessin and Lombardy (and generally south of the Alps) the 

 tendency is to decrease in size. Now this was thoroughly borne 

 out by my own experience, my specimens from Cadenabbia and 

 Eeazzino entirely conforming with the rule, but in the National 

 Collection are a pair from Vallombrosa quite as large as the 

 average of the Ehone Valley, and not differing in colour or 

 markings from many of the brighter specimens from that part 

 of Switzerland ; and, worse still, Mr. Lowe has this year brought 

 home, from Reazzino, large and brilliantly coloured examples, 

 which upset not only my rule, but my actual previous personal 

 experience ! Again, however, it is possible that these facts 

 may be accounted for. The localities both at Cadenabbia and 

 Eeazzino where I took my specimens were very dry ; now much 

 of the neighbourhood of the latter place is very moist, not to 

 say marshy, and, as Mr. Lowe also brought back specimens of 

 britomartis, which is confined to the marshy parts, it is very 

 likely that his athalia came from the same spot ; and, whilst 

 Cadenabbia is dry, Vallombrosa is not. Furthermore, it is a 

 curious fact, for which I am not yet able to account, that the 

 forms of Central Italy are far less southern (paradoxical as it 



