372 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1919. 
Allied to this and almost a part of it, the Museum should furnish 
such conditions of safe preservation that private collectors would 
make it the ultimate repository of their collections. It is an indica- 
tion of progress in this direction that the describing entomologists of 
the country are quite largely sending in their type material, or at 
least paratypes, without waiting to put the gifts in the form of a 
bequest. 
To make its valuable material available to advanced students under 
regulations, liberal yet consistent with the permanent preservation 
of the specimens, is a third function. A large number of entomolo- 
gists visit the Museum each year to study the collection. 
To promote a popular interest in its field through exhibits, lectures, 
etc., is another very clear function. Owing to the fact that the per- 
sonnel of the division is almost entirely derived from the Department 
of Agriculture and has duties primarily economic, but little has yet 
been accomplished in the direction last indicated. 
INSTALLATION. 
The Division of Insects now occupies eight rooms on the third floor 
of the New National Museum Building, with a total floor space of 
6,150 square feet. The space assigned to the various orders is in- 
dicated on plate 1. 
The pinned collections are kept in steel cabinets, constructed in 
units holding 50 glass-covered drawers in two columns of 25, each 
column having two detachable steel doors (pl. 2). The drawers 
are about 18 inches square, and are finished in two styles. In one 
case they are lined with compressed cork and the pins are inserted mn 
this in the usual way; this method is used for butterflies and moths, 
dragon flies, and some other large insects. In the second style the 
drawer is unlined, but is filled with four columns of deep pasteboard 
trays of uniform width and multiple-unit length, which are cork- 
lined. Each species is kept in a tray by itself, which can readily be 
lifted out for study or for rearrangement; the number of specimens 
on hand of the species determines the length of the tray used for its 
reception. 
Alcoholic material is kept in vials in tin-bottomed trays, labeled 
on the end. 
Microscope slides are used for preserving lice, fleas, and some other 
groups where the size is small, as well as for extensive collections 
of dissected genitalia, other anatomical preparations, cast larval 
skins, mosquito larve, etc. This method of mounting seems to be 
increasingly in favor for small insects as higher powers of magnifica- 
tion gradually come into use. 
Type material is recorded under a serial number, which is the 
same for all the specimens of a species. Each specimen bears a red 
