PREFACE. 
The present volume is the fourth of the reports of the Commission, 
and was originally designed as a revised edition of Bulletin 3, and a 
final report on the subject of the Cotton Worm. A single chapter has 
been added on the Boll Worm, because of the importance of this species, 
but other insects affecting the cotton plant are only treated of incident- 
ally. A good deal of material has been collected bearing on these other 
insects affecting the plant, and we hope some day to find time to prepare 
it for publication. But all work except that on the two principal insects 
treated of in this report has been considered of minor importance, the 
main object of the inquiry being as full and accurate knowledge as pos- 
sible respecting those two, especially in reference to their control or 
ready destruction by the planter. 
The sifting of truth from error; the settlement of mooted questions 
by test and experiment; the discovery of previously unknown facts and 
truths, eveu regarding an insect like the Cotton Worm, require an 
amount of labor that few will appreciate who have not experienced the 
difficulties involved ; and whatever merit this report may have is due to 
the fact that the author, in prosecuting the work, has earnestly sought 
to get at the exact truth, wherever there were contiicting views, expe- 
riences, or theories, and because it represents a very considerable amount 
of original research. He has also endeavored to bear constantly in mind 
that the chief object which Congress had in ordering the investigation 
was a practical one, and that whatever purely entomological knowledge 
was acquired, however interesting to the naturalist, was of less moment, 
unless it had some bearing on this practical phase of the subject. 
Hence, descriptive matter and technical discussions are for the most part 
excluded from the body of the work and printed at the end of the vol- 
ume in a series of notes for the benefit of the reader who may be inter- 
ested. Discoveries made in pursuit of some special object often sub- 
serve many other purposes and have wide application* This is emi- 
nently true in applied entomology, and many of the remedies and the 
devices for applying them that have resulted from this Cotton Worm 
investigation are of great use against many other species. This is well 
illustrated in the modern very general use by tanners and fruit-growers, 
in all parts of the couutry, of pyrethram in the field, of petroleum emul- 
sions, and of the cyclone spraying nozzle, all of which have had their 
origin in this investigation. 
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