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Show 1871.] 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 Nephilee, 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 m e 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 concluded 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 m e fairly accounted for by an application of a branch of the principle of " sexual selection." It is the known habit of the female in some Epeirids 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 reference 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 exercise 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). SALTICUS COLLINGWOODII, n. sp. (Plate XLIX. fig. 5.) Female adult, length 2| lines. The cephalothorax (which is of ordinary form) is of a bright reddish 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 posterior 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 respectively than to the former. The falces are moderate in length and strength, a little projecting |