1884.] NEW GENERA OF SPIDERS. 197 



the droppings of a bird ; and is still more remarkable from the in- 

 creased resemblance effected by its spinning of a thin white web on the 

 surface of a leaf, by means of which it secures itself, on its back, to the 

 leaf, leaving its legs free to enclose and seize any insect unwittingly 

 resting upon, or crossing, the apparently innocuous bird-dropping. 

 Mr. Forbes kindly sent me the Spider for examination before writing 

 an account of its habits. I immediately recognized its near affinity 

 to an East-Indian Spider {Thomisus tuberosus, Bl.), of which I 

 possess the type specimen ; but, unable at the moment to make a 

 thorough examination and search through books and specimens, 

 I conjectured that it was allied to some Spiders described by Dr. 

 Karsch, and to one sent to me some years ago from South Africa. 

 A more complete examination since made has convinced me that 

 these latter species (referred to by Mr. .Forbes) belong to entirely 

 different groups. I find, however, in my collection two other Spiders, 

 from Ceylon and Bombay, of the same genus and very closely allied 

 in species, but quite distinct from that which Mr. Forbes notes. 

 Upon these, together with the one last mentioned and Thomisus 

 tuberosus, Bl., I have ventured to found a new genus ; and I beg to 

 record my thanks to its discoverer for so kindly sending me an 

 example of Thomisus decipiens, and for having also made known to 

 us the very peculiar and interesting habits belonging, not only to 

 that Spider, but also, I have little doubt, to the other three closely 

 allied species here described 1 . 



In his description of the habits of T. decipiens, Mr. Forbes ex- 

 presses the difficulty he has in understanding the formation by the 

 Spider of a web which, while serving to attach itself to the leaf, at 

 the same time so exactly represents the fluid portion of a bird's- 

 dropping spread out on the leaf around the more solid parts ; and 

 his concluding sentences appear to imply the inference that the 

 Spider consciously supplements the effects of Natural Selection on 

 its form and resemblance to the solid excreta, by spinning a web to 

 resemble the fluid portion. It seems to me, on the contrary, that 

 the whole is easily explained by the operation of Natural Selection, 

 without supposing consciousness in the Spider in any part of the 

 process. The web on the surface of the leaf is evidently, so far 

 as the Spider has any design or consciousness in the matter, spun 

 simply to secure itself in the proper position to await and seize its 

 prey. The silk, which by its fineness, whiteness, and close adhesion 

 to the leaf causes it to resemble the more fluid parts of the excreta, 

 would gradually attain those qualities by Natural Selection, just as 

 the Spider itself would gradually, and probably pari passu, become, 

 under the influence of the same law, more and more like the solid 

 portion. 



1 Poleschall ('Tweede Bijdrage tot de Kermis der Araehniden van den 

 Indiscken Archipel,' p. 58, pi. xi. figs. 9 and 9 a) describes and figures, also from 

 Java, a Spider (Thom.isu& (tiisimilis, Dol.) possibly of this genus, and perhaps 

 nearly allied to T. decipiens ; but the description is too meagre and general to 

 enable any certain conclusion to be drawn from it, and the figure given of the 

 eyes is totally unlike. 



