50 



PLANT-BUGS INJURIOUS TO COTTON BOLLS. 



cotton when the bolls became more numerous and large enough to 

 be attractive to them. 



The most thorough study of the changes in the numerical status of 

 the conchuelas during July, 1905, was made in a tabla comprising 

 about 120 acres and known as ''Ceceda A 14" (fig. 7). The cotton 

 in this tabla was zoca or seppa, and during the first half of July repre- 



FiG. 7. — Diagram of a portion of the Tlahualilo Cotton Estates. The shaded tdblas are the principal ones 

 referred to in the text. (Original.) 



sented conditions more attractive to the insects than did any equal 

 area of planta (planted) cotton. Five examinations were made during 

 July near the west end of this taUa, beginning with a row about 15 or 

 20 yards from the end and examining across the taUa, changing to 

 next row east, every 10 plants. The results of this examination are 

 summarized in the following table: 



Table XXI. — Variation in abundance of Pentatomids during July, 1905, at Tlahualilo, 



Durango, Mexico. 



When examined. 



Number of 



plants 



per row. 



Number of 

 infested 

 plants 

 m 100. 



Adults per 100 plants. 



Total adult 

 Pentato- 

 mids per 



100 plants. 



Number of 

 nvmphs P. 



P. ligata. 



P. sayi. 



Thyantasp. 



ligata per 

 100 plants.a 



1905. 

 July 11 



100 

 99 

 98 



103 

 96 



19 

 30 

 31 

 12 



52 

 52 

 59 

 33 

 17 





 3 

 4 

 

 





 2 

 

 



52 

 57 

 63 

 33 







15 



13 14 



21 



2 * 



27 







29 



1 17 



12 15 









Total 



Average 



493 

 98.6 



99 

 19.8 



213 

 42.6 



7 

 1.4 



2 1 222 

 . 4 1 44. 2 



1 



6 

 1.2 



a Small figures indicate the instars. 



