i«i6.] 239 



not the slightest resemblance. I have previoussly commented on these 

 careless proceedings (C. R. Ent. Belg., 1885, p. Ixxiv), bnt having since 

 then received Mr. Perkins' fine collection, I have again examined the 

 unique type of Clytus attenioatus, which is novi^ in the British Mu- 

 seum. Boisduval's two lines of contemptible description, and his erro- 

 neous locality, make one hesitate to adopt the name he proposed, but 

 his specimen is of great interest, as being the oldest preserved example 

 of the genus ; Eschscholtz's specimens are 70 years old, and Boisduval's 

 no doubt somewhat older: they do not give us any reason for sup- 

 posing that a change has taken place in the characters of the species 

 of Plagithmysus during the seventy generations of insect life that 

 have been passed through since these examples were secured and 

 preserved. I specially mention this, because when my former note was 

 written an inference of an opposite character might have been drawn 

 from my remarks. Though the greater knowledge I have obtained 

 as the result of Mr. Perkins' successful work leads me to the conclu- 

 sion I have just announced, yet, at the same time, it is only proper to 

 say that the evidence is but slight ; so that though we may be able 

 now to match exactly these specimens three quarters of a century old, 

 yet it is possible that at that time the range of variation of the two 

 species may have been different from what it is at present. 



This brings me to another point on which I venture to offer a few 

 remarks, viz., the variation and distribution of the species of the genus. 

 This is highly remarkable, for whereas the distribution is about as 

 limited as is possible, yet the variation within the tiny realm of each 

 species is in some cases very great. No species of Plagithmysus occurs 

 in two islands ; several species may inhabit one island ; the most 

 closely allied species may exist in the same island, each varying much 

 and each remaining distinct. As regards the variation itself : the 

 sexes ma.j be very different, or they may be almost exactly alike ; 

 the difference between the sexes of a species may be much greater 

 than the differences between allied species : two species may be 

 almost indistinguishable in one sex, and yet quite distinct in the other 

 sex. The variation in size of the individuals of one species is on the 

 average greater than what occurs in species with a wide geographical 

 distribution. In some species the male averages in size larger than 

 the female, in other species the reverse is the case. 



I do not intend to comment on these facts further than to say 

 that they suggest, to my mind, that the specific distinctions are not 

 directly due to geographical isolation, but may be due to a complex 

 of the same causes that have given rise to sexual distinctions, with 



