272 



MOLLUSCA. 



Fig. 143. — Garden Snail (Helix 

 aspersa)^ Reduced h. 



H. virgata and H. raperata, which migrate from the Downs to 

 the fields in numbers at certain times. 



The Garden Snail {H. aspersa), fig. 143, is one of the common- 

 est and most easily obtainable. This large species needs no 



description, as it is well 

 known in every garden. 

 The ova are laid in heaps 

 of sixty to seventy in the 

 earth ; they are white, shin- 

 inc;, globular bodies, which 

 hatch out in fifteen days if 

 kept in the damp. The 

 young are almost colourless, 

 the shell being thin and 

 transparent. Drought and 

 cold are erroneously considered harmful to snails. At the ap- 

 proach of winter they collect together, and exude a slimy matter 

 which hardens and closes the aperture of the shell This cov- 

 ering or lid is called the epiphragm, and must not be mistaken 

 for a permanent operculum. The common snail may be found 

 hibernating together in crevices in walls, in old trees, and under 

 rubbish, u.nited together by the agglutinated slime. 



H. nemoralis, or the Wood Snail, is abundant in hedgerows 

 and upland pastures, especially clover, where it often does much 

 damage. ^ 



In destroying slugs, we must bear in mind the fact that they 

 exude a thick slime which retains any poisonous substance 

 wo may put over them, and which they can cast off. They 

 cannot, however, repeat the violent excretion of the repellent 

 substance more than twice, so that three dressings at short 

 intervals are necessary before we can reach the slug's skin 

 to destroy it. Unless this is done, time and money are simply 

 wasted. I have seen slugs sitting quietly on lime, surrounded 



' For a full cleSLription of injurious MoUusca the reader is referred to a 

 paper by the author in the 'Zoologist' for June 1895. 



