DESTROYING 



187 



advisable, cither sprayed or dusted on, In some cases a mixture of dry 

 dust and kerosene or dry dust (or lime) and sanitary fluid can be applied 

 to the plants ; this acts with plants like cabbage, maize, sorghum, etc., whose 

 leaves are so formed as to hold 

 the powder. Every attack of 

 leaf-eating- caterpillars can be 

 so checked, but the cultivator 

 will not always think the crop 

 is worth the cost of the in- 

 secticide or the labour. The 

 application of insecticides by 

 means of tin sprayers is more 

 readily adopted by market 

 gardeners who grow vegetables 

 for sale in the towns, than by 

 cultivators j every cabbage that is eaten by caterpillars means a loss to the 

 market gardener. 



At present over thirty species of leaf caterpillars are known which 

 attack crops. Many more species will be found, but all have essentially the 

 same habits and life history. 



The question of parasites is a very important one in connection with 

 leaf-eating caterpillars. As a rule when these caterpillars become very 

 abundant, the parasites also increase to such an extent as to kill a very 

 large percentage of the pupae. The result is that few moths hatch and 

 the pest does not reappear as it otherwise would. This is discussed in a 

 later section (page 268). 



FIG. 214. 

 Typical Swarming Caterpillar. 



Swarming Caterpillars. 



It is not unusual to find that large numbers of caterpillars come out 

 suddenly in the fields, ravage the crops and disappear. The caterpillars 



are large, smooth, not hairy, coloured 

 in green or brown usually with stripes 

 along the body from head to tail. They 

 appear in large numbers, eat a variety 

 of crops, and disappear. 



This orm of pest is very similar to 

 the last but is distinct in that the cater- 

 pillars really appear in swarms, and 

 The methods of treating such an attack are 



FIG. 215. 

 Moth of Swarming Caterpillar. 



damage large areas of crops. 



not the same as those used against the ordinary leaf-eating caterpillars, 



