29 



injury by heteropterous insects, principally by the predominatino; 

 species in this particular locality, Pentatoma Vu/ata. The difference 

 in the nature of the damage produced can probably be explained by 

 the difference in the degree of development attained by the bolls be- 

 fore they receive the first injury. 



Injury to Cotton at Tlahualilo in 1904. 



At the time of the second visit of tlie writer to Tlahualilo it was 

 possible to obtain more definite information concerning the character 

 of the injury caused by the conchuela. This was done principally 

 by means of tagging in the field cotton bolls known to have been fed 

 upon more or less by the insect. 



External evidence of injury by this bug never appears, except when 

 a boll is fed upon when 

 very small and one or more 

 locks are injured, so that 

 growth ceases in the injured 

 portions and a deformity of 

 the boll results. The inner 

 side of the carpels of green 

 bolls which have been fed 

 upon by the conchuela 

 show a minute dark spot, 

 indicating the point at 

 Avhich the seta entered, and 

 surrounding this may be an 

 abnormal wart-like growth 

 which is of more frequent 

 occurrence in small bolls, 

 or a smooth circular area 

 which becomes dark green 

 and contrasts sharply with 

 the lighter background. Large bolls nearly mature have been ex- 

 amined with as many as twenty-five or thirty of these spots, but 

 with uninjured seeds, these probabl}^ having been protected by the 

 resistance of the lint to the entrance of the insect's mouth organs. 

 This difficulty probably increases with the increasing age of the 

 boll. In examining smaller bolls it w^as found that a single spot 

 on the inside of the carpel was good, though not positive, evidence 

 of injury, which could be seen only by breaking open the developing 

 lock. In fields where no bugs of any kind could be found none of 

 the bolls showed these spots, while in every case a certain injury to 

 seeds and surrounding lint, which I learned to ascribe to P. ligata 

 and a few less common species of hetero23tera, Avas accompanied 



Fig. 8. — Supposed work of Pentatoma ligata on cot- 

 ton boll (from photo by W. E. Hinds). 



