1905.] 



Slugs and Snails. 



655 



harm now and again, but either they have not been observed, 

 or no record has been made of their depredations. 



Natural Enemies of Snails and Slugs. 



Birds are the greatest natural check to slugs and snails. 

 Almost all birds will devour slugs, but not many will attack 

 snails. The most beneficial is the thrush, which devours the 

 garden snail, cracking its shell against a stone and picking out 

 the mollusc with its beak. The strawberry snail is also a 

 favourite food of the thrush. One frequently comes across 

 little heaps of the shells in gardens, the sides or spire being 

 broken ; these have all been the victims of a thrush. The little 

 hairy snail is also eaten by thrushes, as well as by robins and 

 other birds. The blackbird also eats these mollusca, and many 

 fall a prey to starlings, plovers, and rooks. 



Slugs are attacked also by moles and shrew-mice, and by 

 toads, while numbers succumb to the carnivorous Carabid 

 beetles and their larvae, and occasionally larval Silphidai will 

 devour them. 



Slugs may also be infested with a parasitic mite — PJiilodromus 

 limacns — which swarms over them and stops the formation of 

 slime. Centipedes also attack and kill slugs, while ants are 

 known to kill snails. Both fowls and ducks devour slugs 

 greedily, and the former will eat numbers of snails, even the 

 large Helix aspersa. 



Prevention and Remedies. 



When occurring in large numbers slugs are most difficult to 

 cope with, not only in the field but in the garden. This is due 

 to their being able to excrete slimy mucus immediately an 

 irritant touches them in such quantity that they cast the sub- 

 stance off. This cannot, however, be done indefinitely. Slugs 

 are especially fond of damp situations, and drainage will often 

 lessen their numbers. The mechanical composition of the soil 

 also influences them : a loose open soil favours them, a compact 

 soil is correspondingly unfavourable. I have frequently noticed 

 that slugs are most abundant where an excess of long manure 

 has been used. This should be avoided where slugs are very 

 numerous, and artificial manures used instead for a time. 



