VARIATION AND LOCALITY 121 



bars on the wings, but the female is somewhat thrush-like in 

 colour. In the island of Porto Rico there is a form called xan- 

 thomus, in which both sexes are like the males of the mainland. 

 A similar species called humeralis, also with both sexes male-like, 

 lives in Cuba. The island of Cuba, curiously enough, has also a 

 distinct species named assimilis, in which the female is a dull 

 black all over, though the male is like the mainland type. 



So also may local races differ in respect of variability. Ar- 

 gynnis paphia, the Silver Washed Fritillary, through a great 

 part of its distribution has only one female form. In the English 

 New Forest a second female form, valesina, co-exists with the 

 ordinary paphia female. But in the southern valleys of the Alps 

 the valesina female is much the commoner of the two, and indeed 

 in some localities where the species is abundant, I have seen no 

 paphia females in many days collecting. 



The beetle Gonioctena variabilis furnishes an illustration of a 

 comparable phenomenon affecting the male sex. In 1894 an( i 

 1895 I studied the curious colour variations of this species es- 

 pecially in the neighbourhood of Granada, and Mr. Doncaster 

 ten years later repeated the observations on the same ground, 

 and also collected the insect in other places in the south of Spain. 

 The distinctions are not easy to give in words and the reader is 

 referred to the colour plate accompanying my paper. 5 The 

 essential fact is that the males commonly have the elytra red 

 with black spots and the females for the most part have greenish 

 grey elytra with black stripes. In some localities a large minority 

 of males closely resemble the female type, being identical in 

 colour and then only distinguishable by structural differences. 

 In two Granada localities I found the proportion of such males 

 quite different. In the Darro valley about 38 per cent, (in 



5 Proc. ZooL Soc., 1895, p. 850. Plate. Many points beyond that mentioned 

 above are involved in this remarkable case. For example, not only are there males 

 like females, but a small proportion of females resemble the ordinary male type. 

 The stripes are not merely the spots produced, for they occupy different anatomical 

 positions. The spots almost always go with a black ventral surface, but the striped 

 forms nearly always have that region testaceous. Spartium retama, the food-plant, 

 will not grow in England, but if it could be naturalised in America the whole problem 

 might be investigated there and results of exceptional interest would almost cer- 

 tainly be attained. 



