COTTON 389 



remained dormant, but healthy, for three further months 

 without pupating, and were still in the larval state at the 

 time of writing (April n). The larvae kept at 27 C. had 

 started pupating after nine days, some lingering in the 

 same way as before mentioned as larvae up till the middle 

 of April. 



As all these larvae were kept under exactly the same 

 conditions, heat does not appear to be the factor con- 

 trolling the length of their hibernation or aestivation 

 period. Moisture combined with heat appears to be fatal 

 to them. Of thirty-eight dormant larvae exposed to 

 37 C. in a moist chamber, only two had spun cocoons 

 after ten days, the other thirty-six being dead. The two 

 which spun cocoons died before pupating. Of the larvae 

 kept dry at 37 C., 30 per cent, were dead after ten days, 

 none of those kept at 27 C. died, and only 5 per cent. 

 of those kept at room temperatures. 



No experiments have yet been undertaken to discover 

 whether all the larvae of the summer generations pupate 

 and hatch as adults in short periods, or whether some of 

 them aestivate and pupate later to hatch next year, in 

 the manner followed by the larvae of the previous autumn. 



Gelcchia gossypiella larvae have in Egypt been found 

 feeding on cotton, okroe, or bamiah (Hibiscus esculentus), 

 tehl (Hibiscus cannabinus), and at Mariout on Malva sp., 

 and on pomegranates. Usually the seeds are attacked, but 

 the larvae are also capable of feeding in flower buds. 



It is not possible to detect the presence of Gelechia 

 larvae in attacked bolls without opening the bolls; Earias 

 larvae leave a large hole at the side of the boll or shoot 

 they feed in, and are easily detected by the accumulation 

 of frass below the hole. Exactly how the young 

 Gelechia larvae enter the bolls has not been observed; it 

 may possibly happen through the stigma of the flower, 

 or else the minute hole made by the larvae when entering 

 the boll closes up again. For this reason there is no 

 possibility of combating the insect by pulling off attacked 

 bolls, a method which might be expected to be of help 

 in checking the early generation of Earias. Gelechia 

 larvae also do not damage the cotton in the same way as 

 Earias larvae do. Whilst ordinary boll worm larvae feed 



