DESTROYING CATEBPILI^ARS, 



187 



advisable, either sprayed or dusted on. In some oases a mixture of dry 



dust and kerosene or dry dust (or lime) and sanitary flnid ean 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 iu- 



seeticide 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 



Fig. 214 

 Typical Swarming Caterpillar. 



cultivators ; 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 pupse. 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 368). 



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 form of pest is very similar to 

 the last but is distinct in that the cater- 

 pillars really appear in swarms, and 

 damage large areas of crops. The methods of treating such an attack are 

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



Fig. 215. 

 Moth of Swarming Caterpillar, 



