68 MIMICRY 



aptly named Psyche helix, a kindred species from Italy being 

 known as Ps. ^planorMs. 



An insect larva {Cochlophorcc valvata) from E. Africa is said 

 to resemble a Valvata or young Cyclostonia. In this case the 

 spiral is indifferently dextral or sinistral, the ' shell ' being formed 

 of masticated vegetable matter, united together by threads spun by 

 the larva. Certain larvae of the Phryganeidae (" Caddis-worms ") 

 enclose themselves in houses which more or less resemble a 

 spiral shell, and have in some cases actually been described as 

 moUuscan. Such species, some of which belong to Helicopsyche, 

 have been noticed in S. Europe, Ceylon, Further India, China, 

 Tasmania, New Zealand, Tennessee, Mexico, Central America, 

 Venezuela, Brazil, and Argentina, and all ■ possess a dextral 

 ' shell/ In all these cases ' mimicry ' is probably not so much to 

 be thought of as the practical advantages which accrue to the 

 animal in question from the spiral form, which gives it greater 

 strength to resist external blows, and enables it to occupy, during 

 a very defenceless portion of its existence, a very small amount 

 of space. 



The larva of some species of the Syrphidae {Diptera) fixes itself 

 on the under side of stones in the Tyrol, and closely resembles a 

 small slug. The naturalist Von Spix, in 1825, described to the 

 Bavarian Academy as a new genus of land Mollusca a somewhat 

 similar larval form found in decaying wood on the banks of a 

 German lake."^ Simroth mentions ^ a curious case as occxurring 

 near Grimma. The caterpillars of certain Microlepidoptera occur 

 on slabs of porphyry, associated with a species of Clausilia. 

 Besides being of the same colour as the Clausiliae, the caterpillars 

 have actually developed cross lines on the back, i.e. on the side 

 turned away from the rock, in imitation of the suture of the 

 mollusc. 



It has been suggested '^ that there is mimicry between Aeolis 

 papulosa (a common British nudibranch) and Sagartia troglodytes 

 (an Actinian), and also between another species of Sagartia and 

 Aeolidiella Alderi. The facts observed are not sufficient to 

 warrant a decided opinion, but it seems more probable that the 



1 Von Alarteiis, SB. Nat. Fr. Berl. 1891, p. S3. 



2 Von Martens, ibid. 1887, p. 183. ^ SB. Nat. Gesell. Leipz. xiii.-xiv. p. 45. 



* Garstang, Journ. Mar. Biol. Ass. N. S. i. p. 432 ; Giard, Bull. Sci. Fr. Belg. 

 1888, p. 502 f. 



