CATERPILLAR SWARMS. 



189 



These caterpillars do not occur throughout India ; they are serious 

 pests only when the conditions are favourable and such conditions are 

 not universal in the plains of India. The climatic conditions of Behar 

 and the United Provinces seem to be particularly favourable to them, 

 possibly because the cold weather suddenly gives place to the warm 

 weather when the moths hatch out in abundance. Little is yet known 

 of the occurrence of such swarms of caterpillars but they are likely to 

 occur wherever the conditions favour them. 



A curious feature of these caterpillar swarms is the number of species 

 that are found composing them. Apparently the favourable conditions 

 that produce a large number of one species favour others and we find 

 several species, one in great numbers, others in smaller but still, in the 

 aggregate, large numbers. For this reason also, it is impossible to rely 

 upon the reports and specimens sent in, and as only a few cases have been 

 investigated, little is known of the species which occur in this way. The 

 basis of a swarm is nearly always a caterpillar of the kind known as an 

 "Army Worm," that is a smooth-striped caterpillar (fig. 214), which 

 emerges into one of perhaps six moths 1 of the type figured. With 

 them are for instance the Tobacco Caterpillar (fig. 176), the Sorghum 

 Caterpillar (fig. 156), the Gram Caterpillar (fig. 162), several butterfly 

 and many other moth caterpillars which are typically leaf -eating 

 caterpillars. 



As these pests occur suddenly and not regularly, little has been done 

 to check them or to test the best means of destroying them. The usual 

 methods of applying lead arseniate would be the best if generally avail- 

 able ; this should be done on experimental farms. Other methods depend 

 upon the local conditions. The great thing is to do something quickly ; 

 the cultivator does nothing, because he thinks that caterpillars are sent 

 as a punishment or at least have a miraculous origin. 



When the crops are young or low the usual hopper bag can be used to 

 sweep up the caterpillars (see page 72); discretion must be used in doing 

 this only when the caterpillars are out feeding. When this is not possible, 

 an application of lime and kerosene, road dust and kerosene or other offensive 

 powders may be of use. When the caterpillars are concentrated in a 

 small area, it may be possible to trench all round to isolate them, then 

 apply a mixture or a spray or worry them with a hopper bag till they 

 become restless and move, when they will fall into the trenches where 

 they may be killed. 



1237. Agrotis flammatra. Schiff. (Noctuidw.) 

 238. Euxoa segeiis. Schiff. 

 236. Spodoptera mauritia. Boisd. 



239. Euxoa spinifera. Hubn. 



240. Agrotis ypsilon. Both. 

 110. Caradrina exigua. Guen. 



