Ill MIMICRY o-j 



species of Helicarioyi possess the singular property of shaking off 

 the ' tail ' or hinder part of the foot, wlien seized or irritated. 

 Specimens captured by collectors, Hel. tlgrinus amongst them, 

 have succeeded in escaping from the hand, and concealing them- 

 selves, by a sort of convulsive lea]3, among the dry leaves on the 

 ground. This power of self-amputation must be of great value 

 to Helicarion^ not only as enabling it to escape from the clutch 

 of its enemies, but also as tending to discourage them from 

 attempting to capture it at all. Now the genus Xesta is, in 

 anatomy, very far removed from Helicarion, and the majority of 

 the species are also, as far as the shell is concerned, equally 

 distinct. Xesta Cuyningii, however, has, according to Semper, 

 assumed the appearance of a Heliea?^wn^ the thin shell, the long 

 tail, and the mantle lobes reflected over the shell ; but it has not 

 the power of parting with its tail at short notice. It lives asso- 

 ciated with Helicarion^ and so close is the resemblance between 

 them that, until Semper pointed out its true position, it had 

 always been classified as a member of that group. 



In the same passage Semper draws attention to two other 

 cases of apparent mimicry. The first is another species of Xesta 

 (mind anaen sis') which closely resembles a species of Rhysota 

 (Antonii)^ a genus not indeed so far removed from Xesta as 

 Helicarion, but, as far as the shell is concerned, well distin- 

 guished from it. In this case, however, there is no obvious 

 advantage gained by the resemblance, since Rhysota as com- 

 pared with Xesta is not known to possess any definite point of 

 superiority wdiich it would be worth while to counterfeit. A 

 second case of resemblance between certain species of the genus 

 CMoraea and the chai'acteristic Philippine group Cochlostyla 

 will not hold good as affording evidence of mimicry, for CMo- 

 raea is now recognised as a subgenus of Cochlostyla. 



The Mollusca are not much mimicked by creatures of dif- 

 ferent organisation. This appears at first sight strange, since it 

 might have been thought that the strong defensive house of a 

 snail was worth imitating. Still it is probably not easy for 

 creatures bilaterally symmetrical to curl themselves up into an 

 elevated spiral for any length of time. One or two instances, 

 however, may be mentioned. The larva of a moth belonging to 

 the Psychidae, and occurring in France, Germany, the Tyrol, 

 and Syria, coils itself up into a sinistral spiral of three whorls. 



