74 THE ZOOLOGIST. 



ON SEXUAL DIFFERENCES IN THE WING OF 

 THE HOUSE-SPARROW (PASSER DOMESTICUS). 



By Arthur G. Butler, Ph.D., &c. 



In a short article on the wing of the Sky-Lark, which I pub- 

 lished in ' The Zoologist' for 1898, I expressed my intention of 

 noting the sexual differences in wing-structure of other species. 

 Mr. C. H. B. Grant again assisted me with wings of three male 

 and three female specimens of the domestic Sparrow ; I already 

 possessed five others, and subsequently Mr. F. W. Frohawk 

 added to my collection. I therefore thought I could not do 

 better than select this as an additional example in proof of the 

 fact that, as a rule, the wings of male birds are better adapted to 

 swift flight than those of their mates, thus enabling the former to 

 overtake the latter when courting. 



Of the six wings which Mr. Grant secured for me, all are 

 carefully labelled, but in five of them the important note is 

 added of the actual length of the bird in the flesh from which 

 the wing was removed. As will at once be seen, this is a point 

 of considerable importance, as it proves that, although individuals 

 vary slightly in size, there is no great discrepancy in the total 

 length of the sexes in the flesh. The following are measure- 

 ments of three males : — 



1. Total length . . . 6f inches. 



2. „ ... 6i „ 



3. ,, ,, ... 6£ „ 



Of two females the measurements are : — 



1. Total length . . . 6£ inches. 



2. „ „ ... 6a „ 



Comparing the expanded wings of the sexes in the same 

 specimens, we get the following interesting results : — 



(1. Total length ... 4 inches. 

 3 



Females | Totallen ^ th 



8f 



