NATURE OF INJURY. 17 



relationship in that they occur mth greater frequency on bolls injured 

 by plant-bugs than on those entirely free from injury from this source. 

 Although no external discoloration in the form of spotting of the 

 bolls is known to result directly from the attacks of the representa- 

 tives of the Heteropterous families thus far studied, and included in 

 this discussion, there is frequently present more or less reliable 

 external evidence of damage. Bolls when severely attacked by plant- 

 bugs may flare, turn yellowish, become flaccid, and finally fall to the 

 ground. This has been observed to take place in bolls as large as 

 1| inches in diameter, although it more often occurs in bolls which 

 have attained less than one-half of the normal mature size than in 

 larger bolls. Occasionally a deformity results from the destruction 

 of one lock when the boll is quite small, but this frequently occurs 

 when there is no evidence to connect the deformity with plant-bugs. 

 In addition to these physical changes in the boll, it has been observed 

 with several of the plant-bugs that damaged bolls may be detected in 

 many cases by the yellowish stain produced on the bracts and carpels 

 by the liquid excrement. 



INTERNAL APPEARANCE OF BOLLS DAMAGED BY PLANT-BUGS. 



Description. — Plant-bug injury to cotton bolls can be positively 

 determined only by means of an internal examination. This subject 

 was treated in the author's report^ of preliminary investigation of 

 the conchuela in northern Mexico, but additional observations allow 

 of a more complete consideration at this time. While these observa- 

 tions are for the most part based on the conchuela, it has been found 

 that the same effects result from the attacks of the other representa- 

 tives of the Pentatomidse, as well as the representatives of Coreidse 

 and Pyrrhocoridse upon which studies have been made. The most 

 essential factor in determining injury to cotton bolls by these plant- 

 bugs is the appearance of the inner side of the carpels (PL II, -B.g. 7), 

 where the point of entrance of the insect's setae is marked by a minute 

 dark spot surrounded by a watery or blisterlike, bright-green area, 

 contrasting distinctly with the light, dull-greenish background. In 

 many cases, particularly in bolls three-quarters grown or more, these 

 blisterlike areas increase to a diameter of 4 or 5 millimeters, but in 

 other cases, more especially in small, rapidly growing bolls, a physio- 

 logical reaction in the form of a proliferation of plant tissue takes 

 place. This proliferation (PI. Ill, figs. 6-8) is of the same nature as 

 that which results from the puncturing of the carpels of the bolls by 

 boll weevils, described by Hunter and Hinds in a previous bulletin of 



o Bui. 54, Bur. Ent., U. S. Dept. Agr., pp. 29-30, 1905. 

 22348— Bull. 86—10—^2 



