x INTRODUCTION. 
Mr. Busck has generously allowed me to describe and include in our work a number 
of new species, collected by himself, Mr. F. Knab, and others in the Panama Canal 
Zone and in Mexico, which were not represented in Dr. Godman’s collections, and 
these have afforded strong evidence that only the fringe of the subject has as yet been 
touched, and that the fauna of those regions will prove to be exceptionally rich in 
species and genera. 
I am especially indebted to my friend Mr. W. Schaus for some interesting con- 
tributions to the collection kindly given me many years ago, and the results of his 
energy are further illustrated in the examples submitted by Mr. Busck from the 
National Museum at Washington, to which he has so generously contributed. 
Dr. Godman’s collectors were instructed to obtain insects of all orders, and had 
not the opportunity to devote special attention to the Tineina; consequently a 
large proportion of our material has consisted of unique specimens, which is greatly. 
to be regretted. In the case of these small and often inconspicuous insects, it is 
specially important that a good series of each species should be secured to facilitate 
comparison of markings and structure—the latter almost impossible to certify without 
denudation under the microscope, for which it has sometimes been necessary to sacrifice 
the half of even a unique example. 
In the course of our work one point has been made remarkably clear and 
indisputable. It has been shown by very numerous instances that in the majority of— 
although, of course, not in all—previous attempts to describe and even to illustrate 
differences of neuration, whether for generic or special determinations, reliance has 
been placed on the system of moistening the wings with benzine and examining them 
with ordinary pocket-lenses of varying power, a system which for some of the main 
characters is frequently useful and sufficient. This has, however, proved to be the 
source of innumerable errors, easily detected when the wings are thoroughly denuded 
and placed under the microscope. I must plead guilty to several errors in the past 
from this cause, and the same has affected the work of others upon whose descriptions 
and drawings I have too frequently relied. In the United States this has long been 
recognised. Dr. Brackenridge Clemens (1860, etc.) and other more recent specialists, 
notably Mr. Busck, have invariably made microscopic slides where any doubt could 
exist. In this manner only can the internal veins of the cell, or the different degrees 
of anastomosis and coincidence in the supporting wing-structure, be intelligibly studied. 
Such a method can alone supply the necessary evidence for understanding the processes 
by which gradual changes of development or deterioration have been brought about, 
and this is becoming more than ever essential to correct study. 
