MK. E. I. POCOCK — MIMICRY IN SPIDERS. 257 



Mimicry of Snails and Beetles hy Sliders. 



Amongst the Argyopidse ( = Epeiridse) some species referred to the genus 

 Cydosa resemble small raollnsca which, on account o£ the hardness of the 

 shell, would be eaten by few birds and would certainly be neglected both by 

 PompilidaB and Ichneumonidse, the principal enemies of Spiders, as unfit 

 food for their larvae. One species has been recorded from Ceylon *; another 

 from North America f. The latter, when clinging to the underside of a leaf 

 with its legs drawn up, is almost an exact copy in colour and shape of a small 

 snail which is abundant in similar situations in the same locality during the 

 warm months of the year. The resemblance is enhanced by the complete 

 immobility the spider maintains when forcibly torn from its hold or when the 

 plant is rudely shaken. According to Mr. Shelford J, another spider (Cyrt- 

 aracJme conica) belonging to the same family, and recorded from Kuching in 

 Borneo, also mimics a snail and has the habit of adhering to the underside of 

 leaves. Other members of this family mimic ladybirds (Coccinellidse). 

 These beetles are known to be protected by a nauseous taste. Their short, 

 oval, convex bodies, decorated above with yellow spots on a black ground or 

 black spots on a yellow ground, are closely copied both in form and colour 

 by certain tropical species ; e. €f., by Araneus coccinella, Paraplectana thorntoni 

 and P. icalleri (PL 32. figs. 6, 7, 8), by some East-Indian species of the 

 last-named genus (P. coccinella and P. 12-macidata) , as well as by other 

 species from Brazil and elsewhere. According to Mr. Guy Marshall, 

 Paraplectana thorntoni is, when living, coral-red with black spots, and mimics 

 very exactly a Coccinellid (Chilomenes lunata) common in Natal §; and it 

 was possibly one of the two above-mentioned Oriental species of the genus 

 Paraplectana that Mr. Shelford || cited as mimicking in Borneo the Coccinellid 

 Caria dilatata. 



It is probable that most if not all hard-shelled beetles, whether nauseous 

 like the Coccinellidse or not, are avoided by a majority of insectivorous 

 animals ; and it is still more probable that they are unsuitable articles of diet 

 for the comparatively weak-jawed larvse of Pompilidse and Ichneumonidse. 

 Hence the reason for the imitation of little beetles by the genera CoccorchesteSy 

 Uomalattics, Rliene, and other Spiders belonging to the Salticidas. 



The imitation of short, squat, and compact beetles is probably general and 

 not of particular species of these insects. The resemblance to them displayed 

 by the mimetic spiders is due to the coloration or metallic hues of the 

 thickened integument, to a shortening of the legs, and to the expansion 

 of the cephalothorax and abdomen — the one frequently overlapping the other, 



* 0. P. Cambridge, Encycl. Brit., Araclinida, p. 299 (noted by Col. Yerbury). 



t G. F. Atkinson, Amer. Nat. 1888, p. 545. 



t P. Z. S. 1902, vol. ii. p. 265. 



§ See Pocock, Ann. Mag. Nat. Hist. (7) vol. ii. p. 213, 1898. 



II P. Z. S. 1902, vol. ii. p. 268. 



