58 PLANT-BUGS INJURIOUS TO COTTON BOLLS. 
19,000 acres — would average between 0.063 and 0.079 bale per 
acre. It is certain that this estimate was not too high, as it was 
based solely on the damaged and ruined bolls in evidence in the 
cotton fields at the close of the picking season and no consideration 
whatever was given to the bolls shed as a result of the injury by the 
insects. In the season of 1904 fewer of the bugs were present than 
in the preceding season and the average yield per acre of planted 
cotton amounted to 0.472 bale per acre, being an increase of 0.161 
bale per acre. This increase is believed to be partly due to the differ- 
ence in the number of bugs present in the cotton fields in the two 
seasons referred to. 
In July and December, 1905, field observations throughout the 
plantation of over 22,000 acres at Tlahualilo gave data from which 
it is believed an estimate of damage has been made which is more 
accurate than any estimate of insect damage based on actual field 
examination ever attempted for as large an acreage. It was found 
that bug damage ranged from none at all in restricted areas to 31.6 
per cent and for the entire plantation averaged very close to 8 per 
cent. This does not include the bolls which were shed from the 
plants. These numbered probably less than 2 per cent and their 
loss was not necessarily detrimental to the crop as they did not, 
like those damaged bolls that persisted, continue to receive nutri- 
ment from the plant. The entire yield at Tlahualilo in 1905 amounted 
to about 15,000 bales. The loss of about 8 per cent represents, 
therefore, about 1,200 bales of cotton. The methods used in the 
examinations upon which this estimate is based will be explained 
hereafter. 
A striking contrast to the conditions at Tlahualilo was observed 
about 40 miles distant in the southwestern portion of the Laguna 
district near the cities of Gomez Palacio and Lerdo. Here, for some 
obscure reason, persistent search failed to show the presence of the 
conchuela while other plant-bugs were of remarkably rare occurrence 
in cotton fields. As a consequence plant-bug injury was difficult 
to find and, at the most, amounted to only a small fraction of 1 per 
cent. 
The most detailed study of the losses due to plant-bugs was made 
at the Tlahualilo plantation in 4 blocks heretofore referred to, namely, 
Ceceda A 14, Zaragoza Bl, Zaragoza B2 ; and Zaragoza B3. In the 
first the work extended throughout the block while in the last 3 
blocks the studies were local and represented in each case conditions 
which may have been characteristic of only a small part of the entire 
block of 120 acres. In July, 1905, many examinations of green bolls 
were made for the purpose of determining the percentage of damage, 
