18/1.] REV. O. P. CAMBRIDGE ON ARACHNIDA. 621 



Thwaites from Ceylon. Dr. Collingwood, in his most interesting 

 'Rambles in the China Sea,' p. 189, remarks upon a small Spider 

 which he commonly found in the webs of the large Nephilce, and 

 which, from its small size, he naturally concluded to be of some other 

 species, whose food appeared to be the remains of the larger one's 

 prey. On perusing this account it seemed to me almost certain that 

 the small Spider must be the male of the larger one ; and this opinion 

 was afterwards confirmed by the reception of examples of both the 

 large and small Spiders from Dr. Collingwood, as well as from Mr. 

 Thwaites, who also found them inhabiting the same web, and con- 

 cluded from this and other circumstances that, in spite of the great 

 difference in size, they were the two sexes of the same species. 



Perhaps few points of sexual dissimilarity are more curious than 

 this extreme difference in size between the males and females of this 

 genus, the male being scarcely (in the present instance) more than 

 one-tenth of the length of the female ; it seems to me fairly ac- 

 counted for by an application of a branch of the principle of " sexual 

 selection." It is the known habit of the female in some Epei'rids to 

 endeavour to destroy or devour the male, and M. Vinson, in his 

 work on the Spiders of the Mauritius, speaks of this habit in refer- 

 ence to a species of this genus. M. Vinson gives a very graphic 

 account of the agile way in which the diminutive male escapes from 

 the ferocity of the female, by gliding about and playing hide and 

 seek over her body and along her gigantic limbs : in such a pursuit 

 it is evident the chances of escape would be in favour of the smallest 

 males, while the larger ones would fall early victims ; thus gradually 

 a diminutive race of males would be "selected," until at last they 

 would dwindle to the smallest possible size compatible with the ex- 

 ercise of their generative functions — in fact probably to the size we 

 now see them, i. e. so small as to be a sort of parasite upon the 

 female, and either beneath her notice, or too agile and too small for 

 her to catch without great difficulty. 



Family Salticides. 

 Genus Salticus (Bl.). 



Salticxjs collingwoodii, n. sp. (Plate XLIX. fig. 5.) 



Female adult, length 2| lines. 



The cephalothorax (which is of ordinary form) is of a bright red- 

 dish yellow-brown colour margined by a narrow band of bright 

 shining silvery hairs ; the upper part of the caput is darker than the 

 rest, and is clothed with short yellowish-grey hairs, and a patch or 

 short transverse band of bright scarlet ones between the two pos- 

 terior eyes. 



The eyes are in the ordinary position — those of the third row (the 

 two smallest of the eight) being within the straight line of those of 

 the second and fourth rows, and nearer to those of the latter re- 

 spectively than to the former. 



The falces are moderate in length and strength, a little projecting 



