18 



PLANT-BUGS INJURIOUS TO COTTON BOLLS. 



this Bureau.^ That this abnormal growth may be caused by the 

 punctures of Heteropterous insects was first pointed out by the author 

 in his report of prehminary investigations of the conchuela. ^ Since 

 then^ in the course of more extended investigations of this and other 

 Heteropterous cotton pests, incidental observations on this point 

 have been made by the writer, a summary of which will be found in 

 a publication by Dr. W. E. Hinds dealing with the relation of the 

 proliferation to the cotton boll weevil.^ When caused by the boll 

 weevil, this growth can be easily distinguished from that caused by 

 Heteropterous insects by the distinct open puncture which extends 

 through from the outside of the carpel. The entire inner side of the 

 carpels of bolls damaged by plant-bugs is frequently found on exami- 

 nation to present a rough or papulous surface due to the fact that the 

 punctures are so close to one another that the proliferous growths 

 merge together. At Tlahualilo, Durango, Mex., on July 17, 1905, an 

 examination of 100 injured bolls revealing over 4,000 punctures 

 by plant-bugs (practically all by Pentatoma ligata) developed the fact 

 that 34 per cent of the punctures had resulted in proliferation. 

 On November 1, 1905, an examination of 25 bolls at Dallas, Tex., 

 from a field where three species of Pentatomidse {Nezara Jiilaris, 

 EuscTiistus servus, and Thyanta custator) occurred in considerable 

 numbers, gave the following results in regard to proliferation, using 

 the lock as the unit: 



Table II. — Proliferation on inside of carpels cf lochs fed upon by Pcntatomids. 



Size of 



bolls 



(diameter). 



Locks. 



Number. 



Number 

 showing 

 prolifera- 

 tion. 



Per cent 

 showing 

 prolifera- 

 tion. 



Destroyed 

 by plant- 

 bugs. 



injured. 



Unin- 

 jured. 



Inches. 

 1 -li 

 Total 



60 

 40 



■ 

 42 ! 70 

 11 1 27 



39 



8 



3 

 3 





 a2 



100 



5.3 





47 



6 



2 



1 





a Inside carpels showing three and four punctures, respectively — no apparent injury. 



The objective point of the attack by insects investigated is the 

 seed, which they are able to reach with little difficulty by means of 

 the threadlike organs of their mouth-parts, except in large, nearly 

 mature bolls which are protected by the resistance offered by the lint. 

 Except in the larger sized bolls, therefore, a blisterlike spot or prolif- 



a BuL'51, Bur. Ent., U. S. Dept. Agr., 1905. 



& BuL 54, Bur. Ent., U. S. Dept. Agr., p. 29, 1905. 



c Bui. 59, Bur. Ent., U. S. Dept. Agr., p. 29, 1906. 



