ANIMAL PESTS OF PLANTS 175 



insects, the mature form of the attacking insect, make 

 their appearance. Not only caterpillars, but all kinds of 

 destructive insects may be thus destroyed by other 

 insects, and many species that would otherwise become 

 very injurious are thus kept in check. 



Slugs and snails are best kept in check by hand 

 picking, or by trapping them with cabbage leaves. 



PRACTICAL WORK 



Collect a few caterpillars, together with portions 

 of the plant on which they are feeding. Place these in 

 a box, in the bottom of which is a little garden-mould, 

 to the depth of about ij inches. Cover the box with 

 muslin, perforated zinc, or glass, in such a manner that 

 the caterpillars cannot escape. Supply them with food 

 morning and evening. When the caterpillar changes 

 into a chrysalis, note where the chrysalis places itself, 

 whether it is buried in the soil or whether it attaches 

 itself to the leaves of its food-plant, and note any other 

 arrangement which it makes for its protection. Keep 

 the box with the chrysalides in a safe place until the 

 moths or butterflies appear. Make notes, with sketches 

 of the size, colour, and appearance of the insect in the 

 various stages. Keep an account of the time occupied 

 by each stage. Record the plant on which the insect 

 under observation is found feeding. As many insects 

 as possible should be raised under observation. 



Make a list, which may be added to from time to 

 time, of the insects found upon particular crops, keeping 

 specimens of the insects, drawings or descriptions, with 

 notes of the parts of the plants attacked and of the 



