136 SOME SOUTH INDIAN INSECTS, ETC. [CHAP. XIII. 



avoid the sprayed portions of plants and, rather than eat such, 

 burrow down and feed on the roots. 



Swarming Caterpillars or Army Worms arc so railed because 

 they sometimes appear in immense numbers and, having eaten all 

 the food available in one locality, migrate en masse into crops which 

 they ravage from their mere numbers. Paddy Seed-beds and Grass- 

 lands are especially liable to attack by these caterpillars. The 

 best remedy, as a rule, is to keep them out by trenching. In the 

 case of Paddy Seed-beds these may be flooded if possible anil 

 ducks pi. n n\ in them to eat up the caterpillars. 



Leaf-miners are of little economic importance in themselves. 

 Iln\ live between the upper and lower surfaces of leaves, eating 

 out the green matter and often leaving a tortuous track which shows 

 .is .1 white "mine" on the leaf. The commonest lepidopterous 

 leaf-miner is perhaps Phyllocnistis citrella, whose legless caterpillar 

 mines in young leaves of Citrus. In the case of many Stem-borers, 

 e.g., Chili> simplex in Cholam, the young larva,' may at first burrow 

 into leaves, but these arc hardly leaf-miners in the strict sense. 



Many caterpillars confine themselves to one plant or at least to 

 species of plants which are naturally allied to one another and in 

 dealing with such we can therefore assist control by judicious 

 rotation of crops. But some caterpillars feed on many different 

 plants and are therefore called " polyphagous " (lit. many-eating). 



hi the control of caterpillar pests it is necessary to consider the 

 conditions in which the pupal state will be passed. Many cater- 

 pillars (Kumblipuchis, Cutworms, Army Worms) pupate in the soil 

 and ploughing or suitable disturbance of the ground after they have 

 pupated may sometimes be used in order to destroy the pupa?, 

 cither by exposing them to the sun or to birds or by burying them 

 so deeply that the moths will not be able to escape. Other cater- 

 pillars pupate in rolled leaves, either on the plant or in old dead 

 leaves which have dropped to the ground, ami the collection and 

 destruction oi these will help in reducing the numbers of the 

 sin reeding broods. Stem-borers usually pupate in the stem of the 

 attacked plant, often low down at about ground-level, so that the 

 pupa; are hit behind in the stubble when the crop is cut ; destruction 

 i.l llu stubble is indicated as a remedial measure in such cases. 



