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; PL V, fig. 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. a 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 6 and their general economic importance and their life 
a American Naturalist, XLI, pp. 417-430, 1907. 
6 Bui. 64, Pt. I, Bur. Ent., U. S. Dept. Agr., pp. 9-10, 1907. 
