56 THE entomologist's record. 



times all three bumping together and then swinging off again. Then a 

 fourth came down from the top of the bank and joined in the game. 

 They were so intent upon it they allowed me to stand so close that I 

 could have touched them with my hand. At last I netted the four at 

 a single stroke, and, immediately repenting I had disturbed them, I 

 turned them out of the net. One flew away, but the other three actually 

 returned to their play, and I left them there. Sometimes only two 

 would collide, often three, but generally before they parted all four 

 would be in close proximity if not in actual contact. They were rather 

 clumsy, and it seemed as if they needed to swing backwards and for- 

 wards once or twice before they could steady themselves sufficiently to 

 direct their flight as they wished. Before I leave this species I would 

 call attention to the fact that it is the only one of our " Swifts " in which 

 the sexes differ in a very marked degree,^ and, also, that the males 

 occuring in the Shetland Islands, known as var. hethlajidica, are much 

 more like the female than the ordinary form. So long ago as 1865, Dr. 

 Knaggs called attention to the peculiar form hunmli assumed in these 

 Islands {Ent. Ann., 1865, p. 98), but little notice was taken of the 

 matter, and it was not until Mr. Meek's collector, some years later, 

 brought a large number of these extraordinary specimens home, and 

 they became generally distributed in our collections, that we began 

 generally to understand what it was to which our attention had been 

 directed. Some said that in these remote Islands the male had 

 assumed the markings of the female, but another explanation of the 

 phenomenon is more probable. All our British species of Hepiabis are 

 similar in character of markings except male hunmli, which (except these 

 varieties) is without markings entirely. This indicates descent from 

 one ancestor, and it is more than probable that the sexes of hunmli 

 once resembled each other, as do the sexes of the other species. The 

 female flying to the male by sight would always see the paler specimens 

 best. Thus, the lighter the colour of the males, or the more silver 

 there was about them, the more conspicuous would they be, and, 

 therefore, more likely to secure partners and produce a lighter or more 

 silvery offspring. This would go on year after year, the silvery markings 

 increasing in extent in the course of generations, until a perfectly white 

 male was produced as we see it now, solely by " natural selection." 

 In the extreme north, where there is longer daylight at midsummer than 

 with us, the female would be able to see better than in our dim twi- 

 light, and the paler males would have less advantage. The process of 

 selection, therefore, would be slower, and as the darker males, as Lord 

 Walsingham has shown, would develop more rapidly, still tending to 

 delay the evolution of the perfectly white male. {To be continued.) 



Variation. 



Variation in Midlothian Lepidoptera. — Spilosomafuliginosa, L. — 

 I have only taken a few specimens of this insect, one of which, captured 

 on June i6th, 1888, had a perfect, though diminutive, left upper wing. 

 Mr. W. Evans has also taken them in the bog. Panolis piniperda, 



^ I have always looked on H. sylviims as presenting very marked sexual dimor- 

 phism. — Ed. 



