COTTON STEM BOP EH, 



wither, turn yellow and (lie, apparently 

 without cause. If such plants are pulled 

 up and broken across at the crown, it 

 will be found that the centre has been 

 eaten out, a round tunnel extending up 

 and down the thickest part of the stem. 

 Possibly the insect causing this damage 

 will be found inside the tunnel, and there 

 can then be no doubt as to the iden- 

 tity of the insect. No other insect 

 is known to attack cotton in this way in 

 India, and if such bored cotton stems are 

 found without the insect, search for other 

 withered or dying plants will probably 

 reveal a plant with this insect at work. 



Life History. The grub enters the 

 stem near the crown, hatching from an 

 egg laid there by the beetle. It bores 

 into the stem, feeding upon the tissues as 

 it goes, and making a neat round tunnel 

 up and down the centre of the stem. One 

 grub inhabits a cotton plant and its tunnel 

 sooner or later destroys so much tissue 

 that the plant dies. The grub is white, 

 in length up to one inch, with a slender 

 body, very much swollen into a round, 

 slightly flattened bulb at the front end. 

 The head is small, in front of the swollen 

 thorax, and has powerful jaws with which 

 it gnaws away the wood. Legs are absent 

 and the bulbous swelling fits the burrow in 

 such a way that the larva can move by mus- 

 cular contractions and expansions of this part. 



When full grown the grub eats a hole 

 almost to the outside, leaving the bark 

 intact, and turns to a chrysalis within the 

 burrow. The chrysalis is white, becoming 

 dark before it emerges, and the legs, wings 

 and antennae of the future beetle may be 

 seen folded against the body. It lies 

 jnotiojiless within the burrow whilst the 



101 



FIG. 114. 



Stem Sorer in Cotton 

 Stem. 



