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I^OCAIi EXTERMINATION. 



Many insects increase with amazing rapidity from the compara- 

 tively few individuals which pass the winter successfully to the 

 countless thousands at the close of summer. The bollworm offers a 

 good example of this, although the increase in its case is not so strik- 

 ing as with some other insects. 



It has been estimated by Messrs. Quaintance aiiti Brues, from 

 observations made during 1904, that in the third generation the 

 larvae resulting from one female emerging the previous spring would 

 number 21,175; or one larva of the first generation will give rise to 

 G83 descendants in August — a sufficient number to completely ruin 78 

 large cotton plants. In making these calculations due allowance 

 was made for destruction in the different stages by various natural 

 agencies. From these figures the importance of destroying the 

 larvae of the early generations is very apjjarent. 



Experiments conducted at Quinlan, Tex., and Atoka, Ind. T., dur- 

 ing 1905 indicate that in isolated localities almost complete freedom 

 from boll worms in cotton may be secured by destroying the larvae 

 of the first and second generations in all adjacent cornfields. 



Various mechanical devices have been suggested for use in de- 

 stroying larvae in corn ears. The writers have given the subject 

 some attention, but have been unable to devise any satisfactory scheme 

 for killing the larvae without opening the ears by hand. When 

 mechanical devices are used the ears are often greatly damaged and 

 in many instances the larvae escape. 



In the experiments conducted ver}^ few larvae of the first generation 

 were seen in the young corn, and the fields were not carefully gone 

 over at that time; however, nearly every ear was infested by the 

 second brood, as is shown in the accompanying table. In case of the 

 Mineola record, ears upon which eggs were deposited were not 

 included in the number of those infested. Had these been included 

 with the number of infested ears, as should have been done, the 

 infestation would haA^e reached about 92 per cent. 



Table A'I. — Bollworm larvte in corn and cost of extermination. 



At Quinlan the larvae were extracted from the ears on about 3 

 acres of corn and at Atoka from about 2^ acres. About 7^ acres of 



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