344 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
larvae are predaceous on the woolly alder aphid (Prociphilus tessel- 
latus (Fitch) ) are beneficial. 
The feeding habits of the lepidopterous larvae vary greatly, but by 
far the greater number are plant feeders. They may attack the foliage 
of forest and shade trees as miners or skeletonizers, or devour it com- 
pletely, or act as miners or borers of buds, stems, twigs, bark, or wood. 
Some stage of these insects is present at all times, but the injury may 
pass unnoticed unless an outbreak occurs. Various factors affect their 
economic importance, particularly the nature and extent of injury, 
whether they are general feeders or are restricted to certain food 
plants, and the value of the plants or products attacked. 
In the eastern part of the United States there are more than 5,000 
species representing more than 60 families of Lepidoptera. Compara- 
tively few of these species, however, attract attention as serious pests 
of forest and shade trees and shrubs; therefore only the families and 
species that are generally most common are discussed herein. The 
species are grouped systematically under their respective families, 
the arrangement following that used in the United States National 
Museum. 
The wealth of material at the New Haven, Conn., laboratory of the 
Bureau of Entomology and Plant Quarantine has aided materially in 
the preparation of this section of the manual. This material, both in 
records and specimens accumulated from many years of collecting and 
rearing of lepidopterous larvae, resulted from studies begun in 1915 
at Melrose Highlands, Mass. Various publications, not all of which 
are listed in Literature Cited, p. 637, have been consulted freely for 
further information on many of the families, genera, and species. 
In their life cycle, Lepidoptera undergo a complete change, or per- 
fect metamorphosis, passing through four stages as follows: Egg, 
larva or caterpillar, pupa or chrysalis, and adult. These various 
stages have been discussed by Comstock (703), Forbes (/65), and 
Holland (228, 229). 
ADULTS 
The minute scales covering the wings and body of the adults are a 
distinctive feature of this order. These scales overlap like shingles 
on a roof and are of many shapes, ranging from hairlike structures to 
short and broad scales. The mouth parts are formed for sucking, as 
the food consists only of liquids, such as nectar from flowers, juices of 
overripe fruit, or honeydew. The adults of many species, however, 
do not take any nourishment, and their mouth parts are poorly devel- 
oped, probably from disuse through countless generations. 
Although the order Lepidoptera is popularly divided into the two 
groups of butterflies and moths, this division is not based on a natural 
classification. In general, it may be said that the butterflies have 
antennae which are alike in both sexes, being long and threadhke and 
usually with a club at the tip. They fly during the daytime, and when 
at rest the wings are folded together in a vertical position over the 
body, except for some of the “skippers,” whose forewings are held in 
a vertical position while the hind wings are folded horizontally. The 
moths differ from the butterflies in that the antennae are usually 
threadlike or featherlike and without a club at the tip. They have 
a tendency to fly by night, and most species are attracted to lights. 
The wings of moths are folded rooflike, held in a horizontal position, 
or wrapped around the abdomen when at rest. The females of some 
