THE ZOOLOGIST 



No. 709.— July, 1900. 



SPINNING MOLLUSCS. 



By H. Wallis Kew. 



(Plate III.) 



The production of a mucus-thread, as a means of progression 

 through the air, has long been known in the Land-Slugs, and has 

 been observed in seven genera, representing Limacidce, Arionidce, 

 and Philomycidce. 



The Spinning-Slug {Limaxfilans) of authors is a myth, the 

 habit being general, extending possibly to all Slugs of the families 

 named. The animals are occasionally seen descending from trees, 

 fences, rafters in greenhouses, &c, and they are easily induced to 

 descend from small exposed objects on which they may be placed. 

 They crawl from the object, and, when the tail parts company 

 with it, the animal is sustained by a thread, which is left by the 

 body at the tail, and is gradually lengthened. Sometimes the 

 animal thus reaches a new support without a fall, but the faculty 

 is imperfect, the animal often falling either without a thread or 

 after making a short one. Large Slugs, when full-grown, are 

 incapable of this kind of locomotion ; but small ones, and the 

 young of large kinds, are occasionally capable of making success- 

 ful descents of surprising length. Threads measuring 3-7 ft. 

 have several times been observed, and others 8-9 ft. long have 

 been reported. 



On the foot of the descending animal wave-like appearances 



Zool. 4th ser. vol. IV., July, 1900. x 



