SOME SOUTH INDIAN INSECTS, ETC. [CHAP. XVI. 



leaves, fruits or roots of plants, although the life-histories of very 

 few arc known in India. 



Ih. Cotton Stem Weevil (Pempheres qffinis) lays its eggs on 

 stilus of young cotton-plants at about ground-level and the larva 

 makes .1 spiral burrow inside the stem which produces a character- 

 istic gall-like swelling, inside which it lives and pupates. In the 

 case of badly-attacked plants the whole plant may be snapped off 

 by the wind. No successful remedy, applicable on a field-scale, 

 has been found hitherto, but in the case of experimental plots 

 painting the stems with crude oil emulsion may be recommended. 



The Sweet Potato Weevil (Cylas formicarius) bores into the 

 tubers of sweet potato which it utterly ruins, every tuber being 

 bored and rotten in the case of a bad attack. No direct remedy is 

 applicable. The beetles are easily collected by hand-nets or bag- 

 nets as they sit on the leaves of the food-plant but the damage has 

 usually been done by the time that they are noticed. Abandoning 

 the cultivation of sweet potato for at least a year after an attai k. 

 and the use of deeply-rooted varieties of plants, will help to prevent 

 attack. The infected tubers may be fumigated or may be boiled 

 and fed to cattle. 



The Mango Weevil { Cryptorhynchus mangiferal) which passes its 

 life-cycle inside the stone of a mango fruit, is very common, 

 probably ninety per cent, of mangoes being infected in some years, 

 although as a rule the presence of the beetle passes unsuspected 

 and no damage is done to the fruit itself. If the stone of a ripe 

 fruit is cut open, the beetle itself, or its larva or puna, will generally 

 be found. 



Many weevils are leaf-eaters as adults and may do damage, 

 usually of a minor nature, to crops. They are generally easily 

 collected by shaking the plants over cloths or pans of oil-and- 

 water; it should be noted that weevils, when disturbed, frequently 

 drop to the ground and "sham dead " and this death feint should 

 not lie mistaken for the real article. Many weevils also have such 

 an extremely tough and thickly chitinized integument that they are 

 not killed by treading on them with the foot on ordinary soft soil 

 and care must be taken to see that they are really squashed. 



