CHAPTER VIII. 



PESTS OF THE COTTON PLANT. 



THE cotton plant suffers from a number of insect pests which lessen the 

 vigour of the plant and diminish the actual yield of the lint and seed. 

 These pests are widespread in India, do a great aggregate amount of 

 damage and largely reduce the yield of probably every acre in India ; but 

 they are disregarded by the cultivator, who is not aware that he can, by 

 adopting simple measures, obtain a larger yield of finer cotton. These 

 pests include the boll-worms, of which there are three species, two 

 identical in almost all but name and one distinct species ; the two beetles 

 that attack the stem ; two bugs that attack the bolls ; and two caterpillars, 

 an aphis and a leaf -hopper, that attack the leaves. There are in addition 

 a variety of minor pests which are not exclusively pests of cotton and 

 which appear only casually. 



The Spotted Boll- worm. 



Caterpillars which destroy ripening bolls of the cotton plant and 



which may be found by looking for such 

 jfi>^ j-- injured bolls before the cotton ripens. They 



J?7 i-' are easy to recognise and readily reared to 



the imago. The life history is typical of 

 the moths. 



The term boll- worm is in America applied 

 to the caterpillar described in this book as the 

 Gram Caterpillar (see page 144). In India 

 this insect does not attack cotton, its place 

 being taken by the two spotted boll-worms 

 and the pink boll-worm, the latter being 



Soil containing Boll-worm. 



discussed separately. 



Life History. Eggs are laid by the moth singly on the bracts, bolls 

 and terminal leaves of the cotton-plant. Each egg is small, not more 



Figures. Where a figure is said to be magnified, and a hair line is found beside the 

 insect, this line represents the actual length of the insect as drawn. When there is no hair 

 line, the statement, for example " magnified three times," means that each lineal dimension 

 ia three times larger in the figure, the figures being thus actually nine times magnified if 

 we consider the area it covers. A linear magnification of even three is considerable, and in 

 comparing an insect with a figure (in the endeavour to identify the insect with the figure) 

 a good lens must be used ; the human eye cannot compare a small insect with its enlarged 

 figure unless the insect is ^resented to it at least as large as the figure. A lens magnify ing 

 ten diameters will be sufficient for every insect figured in this volume, but it is impossible 

 to compare insects and tie figim-s niilses a lens is used. Where no magnification is 

 mentioned and no liair line occurs, the figure is the natural size. 



