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De MISC. PUBLICATION 198, U.S. DEPT. OF AGRICULTURE 
of Agriculture, Arts, and Manufactures; Massachusetts Society for 
Promotion of Agriculture; and Memoirs of the Philadelphia Agri- 
cultural Society. Probably the writers whose observations were most 
dependable during those years were G. Morgan (1787), P. Muhlenberg 
(1788), L. Carter (1789), A. Young (1789), Thomas Jefferson (1792), 
William Kirby (1798,1800), J. Cooper (1799), C. A. LeSueur (1817), 
Thomas Say (1817, 1818), J. H. Cocke (1819), Edward Tilghman 
(1820, 1825), and Kirby and Spence (1822). In the decades subse- 
quent to 1825 the references became sufficiently numerous and variea 
to render specific mention impracticable, except for certain outstand- 
ing articles, as those by H. C. Herrick (1841), Asa Fitch (1846), Kirby 
and Spence (1846), A. S. Packard (1878, 1880), and S. A. Forbes 
(1887-90). Other writers who at various dates made noteworthy 
additions to the history cf the investigation included such individuals 
as C. V. Riley, Cyrus Thomas, F. M. Webster, Lawrence Bruner, ° 
C. J. S. Bethune, and Albert Koebele. 
Obviously, only a part of the foreign literature could be included, 
not only because of the mere limitations of space and bulk but also 
because a complete examination of European literature could best be 
made by a bibliographer having access to the principal libraries of the 
Old World, and by one more familiar than the compiler with the vari- 
ous languages in which the facts are recorded. It is equally obvious 
that not all of the foreign literature could be omitted without seriously 
detracting from the purpose of the present compilation and lessening 
its value, particularly in the studies of the distribution of the pest 
and its strictly historical aspect. Only those foreign references, 
therefore, which are of particular usefulness to workers in this country 
have been included. 
The scope of this publication does not permit the inclusion of refer- 
ences to literature dealing with the synonymy of hessian-fly parasites, 
except insofar as such references also contain data on other phases of 
the hessian-fly investigation, since full treatment of the literature on 
synonymy of parasites is given by Gahan (429). 
Of necessity, a number of articles have been listed which repeat 
facts already stated. This has been necessary because of other infor- 
mation in the articles, as notices of local outbreaks and data as to the 
presence of parasites, the spread of the pest in given years, or special 
control demonstrations. In a number of instances, but not always, 
inclusive pagination is given instead of the first page or that on which 
the particular reference appears. This procedure has been deemed 
most useful for quick reference because of variation in pagination 
in the different publications in which some of the writings, notably 
certain State experiment station reports, were issued. 
It has not been considered feasible to include the numerous valuable 
references on the hessian fly contained in the Insect Pest Survey 
Bulletin, a monthly review of entomological conditions throughout the 
United States, prepared by the Bureau of Entomology and Plant 
Quarantine of the United States Department of Agriculture with the 
cooperation of State entomological agencies, as this work is issued 
only in mimeographed form and is of a character so ephemeral that it 
probably would not be permanently preserved by a large number of 
libraries widely distributed throughout the country. However, im 
order to insure completeness of data, investigators studying the 
progress of hessian fly investigations in the United States since May 
1, 1921, should review the Insect Pest Survey reports. 
