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Show 1903.] A NEW SPIDER FROM CEYLON. 51 and Green was resting upon the leaf in the normal position, that is to say back uppermost (figs. 1 & 2). Forbes, however, expressly states that P. decipieus, the species he discovered, lies back downwards on the web, holding itself in place by means of the spines with which the anterior upper surfaces of the legs are furnished, and he adds that the underside of " its rather irregularly-shaped and prominent abdomen is almost all white, of a pure chalky white " (p. 587), and that " its pure white abdomen represents the central mass of the bird's excreta, the black legs the dark portion of the slime." Reference, however, to his figure, which was apparently drawn partly from memory, the leaf and web having " gone astray " during the transport home, shows that the underside of the abdomen, so far from being almost all white, is furnished with a large black sub-oblong patch, which extends from its anterior border considerably past the middle. It is noticeable, too, that from the ventral aspect the abdomen is not irregularly shaped, but evenly oval in outline and devoid of tubercular excrescences. The dorsal surface, on the contrary, as represented in the figure given by Mr. Cambridge (P. Z. S. 1884, pi. xv. fig. 1), might very well be described as almost all white and rather irregularly shaped. The white colour largely predominates, and the tubercles project prominently from the expanded posterior portion. Mention is made of these discrepancies between the figure and description, to justify the suspicion that Dr. Forbes may have mistaken the dorsal for the ventral surface of the spiders he saw. Moreover, one cannot but wonder how the spider maintains a secure hold back downwards, especially when the powerful preliensorial legs of the first and second pairs are released, as released they must surely be, to seize an alighting butterfly. One would think that the flapping of the insect's wing would pull the spider, now insecurely anchored, from its hold and bring both to the ground together. On the other hand, if the spiders of this kind always rest in the normal position seen and photographed in the case of P. rothschildi, the simulation of the bird's-dung is equally perfect, and the spider, while seizing a butterfly with its fore legs, can maintain itself securely in place by grasping the web with the claws of the remaining pairs and by gluing its spinning-mamillse to the subjacent silken threads. These, then, are the points for further investigation which we would ask residents in the tropics to take note of :- Do the species of Phrynarctchne assume indifferently the dorsal or the ventral attitude ? Is it a peculiarity of one species to lie back uppermost, and of another belly uppermost ? If they lie, as Forbes asserts, back downwards, how is a secure hold maintained when an insect has to be seized ? EXPLANATION OF PLATE X. Phrj/naracline rothschildi, sp. n., p. 48. Figs. 1, 2. The Spider resting on leaf. Fig. 3. Upper surface. Fi°\ 4. Under surface. Figs. 5, 6. Eyes. 4 * |
