174 NATURE TEACHING 



animal. Snails and slugs lay eggs in damp places, on 

 leaves of plants, etc., and from these hatch directly young 

 snails or slugs, there being in this group no stages cor- 

 responding to the larvae or pupae of insects. 



Most snails and slugs feed on vegetable matter, and 

 their ravages in gardens are familiar to every one. The 

 garden snail and the ordinary grey slug are to be found 

 in almost every garden, and in fields the large black slug 



is often met with. 



Remedies. 



In order to limit the damage done to crops by 

 injurious insects, various steps may be taken ; first of all 

 the eggs of butterflies and moths when seen upon leaves 

 should be destroyed, and the caterpillars should be 

 picked off and killed. When these remedies are 

 inapplicable .various insecticides may be dusted or 

 sprayed upon the plants attacked. Full directions con- 

 cerning the use of many of these are to be found in the 

 excellent leaflets of the Board of Agriculture, obtainable, 

 free of charge, on application to the Secretary, 4 White- 

 hall Place, S.W. 



Many caterpillars are kept in check by being 

 attacked by other insects which lay their eggs in their 

 bodies. The insects attacked are not immediately 

 killed by this operation, which commonly takes place 

 in the caterpillar stage, but the caterpillars often live 

 and pass into the chrysalis stage. . By this time the 

 larvae of the insect which has attacked them have 

 hatched out and usually kill their host by feeding on it 

 in this stage, so that instead of the expected moth or 

 butterfly issuing from the chrysalis, a number of flying 



