62 PLANT-BUGS INJURIOUS TO COTTON BOLLS. 



At Tlahualilo the crop of 1902-1903 included 1,277 bales of cotton, 

 or 11.2 per cent, grading below '^strict good ordinary," and classed 

 as ^'stained." The crop of 1903-1904, which was damaged by bugs 

 to greater extent than any other crop, included 1,812 bales, or 23.5 per 

 cent, of this class of cotton, while the crop of 1905-1906 included 885 

 bales, or 6.6 per cent. Near the cities of Lerdo and Gomez Palacio, 

 in another section of the Laguna district, as has been heretofore stated, 

 the conchuela was apparently entirely absent and other Heteropterous 

 insects were of exceptionally rare occurrence in cotton fields. Stained 

 cotton in the fields in this locality is either difficult or impossible to 

 find. A plantation near Lerdo, belonging to the same company as 

 the one at Tlahualilo, produced over 2,000 bales of cotton as the crop 

 of 1905-1906. The author's field observations as to the absence of 

 plant-bugs and stained cotton in these cotton fields in July and 

 December, 1905, received verification in the classification of baled 

 cotton by the buyers, inasmuch as not a bale of the entire crop was 

 classed as ^'stained." 



NATURAL CONTROL. 



Weather Influences. 



Hard rains doubtless destroy many young Pentatomid nymphs, 

 but such rains seldom occur in the regions where the conchuela is 

 most abundant. At Tlahualilo, after an unusually heavy rainfall in 

 July, 1905, Mr. J. A. Vaughan found nymphs in large numbers crawl- 

 ing on the ground along the banks of an irrigation canal several miles 

 from the cultivated fields. These nymphs were mostly in the fifth 

 instar and had undoubtedly been beaten from the mesquite by the 

 rains. Two results of importance might follow such an occurrence: 

 First, a large number of the nymphs might die without reaching food; 

 second, the nymphs thus forced to migrate might overrun cultivated 

 lands with serious effect upon the crops. 



Parasites Attacking Eggs. 



The writer has recently described as Telenomus ashmeadi Morrill 

 (fig. 8; PI. V, ^g. 2), an important species of egg-parasite which has 

 been found, both in western Texas and in Mexico, to effectively check 

 the multiplication of the conchuela by midsummer.^ The seasonal 

 history during several years as noted by reliable observers indicates 

 that this result is accomplished with considerable regularity. Were 

 it not for these insects, damage to cotton at points in the Laguna dis- 

 trict in Mexico and western Texas would be so great that this crop 

 could not be profitably produced. The importance of these insects 

 in western Texas in 1905 has been discussed by the writer in a previ- 

 ous bulletin^ and their general economic importance and their life 



« American Naturalist, XLI, pp. 417-430, 1907. 



6 Bui. 64, Pt. I, Bur. Ent., U. S. Dept. Agr., pp. 9-10, 1907. 



