PREFACE. 
The World's Columbian Exposition, held in Chicago in 180.3, served as 
the medium of importation of several species of insects of then imper- 
fectly known distribution and habits, and incidentally much information 
was gathered from the collections made by the writer in tbe foreigD agri- 
cultural exhibits that were displayed there. Similarly the Cotton States 
and International Exposition, held at Atlanta, Ga., in 1895, became the 
means by which knowledge of new food habits and habitat for a few 
species of doubtful or unknown habits and obscure origin has been 
gained. The material and other data obtained at the Columbian Expo- 
sition in stored products served as an impetus to the investigation of 
this group of insects and the living specimens in their food material 
obtained there, augmented by additions through correspondence and 
collections made in the city of Washington, have been under more or 
less continuous observation since. Certain of the preserved material 
has also received study, in connection with related forms, as time and 
opportunity afforded. 
In the spring of 1894 the writer was directed to prepare a bulletin 
covering the subject of the insects affecting stored cereals. At the out- 
set it was necessary, as a preliminary step, to properly identity the 
species to be considered. A number of radical changes have recently 
been made in the previously accepted nomenclature of these insects, 
involving the separation of species hitherto considered under a single 
name, the restoration to the species of the earliest published names. 
and the indication of synonyms. 
Since its original inception the scope of the work has been enlarged 
to include insects affecting other stored products than cereals, and ii 
has been thought advisable to compile as complete a bibliographical 
list of important references to each species as can be secured. 
The preliminary labor involved in the preparation of such a work has 
consumed much time and is still in progress. It comprises the perusal 
of all available literature, including the indexing and digesting of nam- 
berless notes and articles, mostly scattered through periodicals and in 
many languages; the procuring of living specimens for rearing, and 
observation of the various species to be treated; the comparative 
Study, description, and illustration of these species in all their various 
forms from egg to adult; the rearing and identification of parasites; the 
ascertainment of the character of the injury o( the different species. 
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