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JOURNAL OF MALACOLOGY. 



No. 2. JUNE 25th, 1S94. Vol. III. 



ON A CASE OF PROTECTIVE RESEMBLANCE 

 AMONG SLUGS. 



By G. SHERRIFF TYE, 



Haiuhivorth, Rirntii2i:;haiii. 



I WISH to call attention to the very remarkable likeness existing 

 between Avion /lorfensis and As^rioli/nax agrestis, and portions of the 

 bloom sheath of the black poplar {Popuhts nigra, L.). 



On April 1 2th, while in the garden, I noticed what I took to be 

 a number of these slugs lying among what I knew to be the bud- 

 sheaths of the poplar overhanging my fern-house. They were close 

 against the garden tiles along the edge of the lawn ; there had been 

 some rain and the ground was damp. I thought this a fair oppor- 

 tunity for giving our pet thrush and blackbird a treat, so I " went " 

 for these slugs, but was surprised to find that I had been deceived — 

 they were poplar bud sheaths. 



In thinking upon the matter the conclusion was forced upon me 

 that in the slugs we have a strong case of protective mimicry. 



Not all the sheaths — perhaps 30 per cent. — bear a wonderful, 

 I might almost say an exact likeness of either one or other of the 

 species named, and all bear such a semblance as to act as an 

 efhcient concealment to the slugs when 'lying among them. The 

 fact that only a percentage were so truly slug-like lent greater point 

 to the concealment. 



Sometimes the smaller portion (lower) of the slieath, which 

 adheres by the gummy secretion of the bud to the larger upper and 

 inner part— giving the mantle to the false slug — falls off, yet even 

 then, for a time at least, unlil age darkens ir, the lighter part where 

 it was inserted carries out the deception. 



Journal of Malacology, Vol. iii., No. 2. 



