410 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
Foop PLants oF THE Gypsy Moru.—Apple, speckled alder, bass- 
wood, gray and river birch, hawthorn, oaks, poplars, and willows are 
most favored by the larvae of the gypsy moth. Species distinctly less 
favored, though eaten by the larvae in all instars, include black birch, 
paper birch, and yellow birch, the cherries, chestnut, elm, black gum, 
hickories, hor nbeam, larch, maples, and sassafras, Species not fa- 
vored by the young larvae but favored by the larger larvae include 
beech, hemlock, southern white cedar, and the pines and spruces na- 
tive to the eastern part of the United States. Those species of trees 
not at all favored as food include.ash, balsam, butternut, black walnut, 
catalpa, red cedar, flowering dogwood, American holly, locust, syca- 
more, and yellow poplar. 
SrasonaL History anp CHARACTER OF Work.—The moths emerge 
and mate, and the females deposit eggs late in July and in August. 
The winter is passed in the egg stage, and hatching takes place about 
the first of May. The larvae spin down on silken threads, and the first 
instars may be borne long distances by the wind. The greatest dis- 
persion by wind occurs on hot days when convection currents from the 
heated surface of the ground are prevalent. Pure stands or mixtures 
of the favored species or stands contaiming mixtures of favored spe- 
cies, and some of the less favored, may be completely defoliated, but 
the ereater the proportion of the latter class, the less danger there is 
of an infestation building up enough to cause serious defoliation. The 
larvae pass through five ‘and six instars for the males and females, re- 
spectively, becoming full grown late in June or early in July. The pe- 
riod in the pupal stage is about 10 days to 2 weeks. 
Economic Fratrures.—Although outbreaks, both regional and local 
in character, now occur at more irregular intervals in New England 
since the introduced parasites have become established, this pest still 
causes more or less defoliation over thousands of acres of forest growth 
each year. An infestation may exist for several years in a farm wood- 
lot or a large forest without causing sufficient defoliation to attract 
attention, because of the influence of the various natural control fac- 
tors, and then may suddenly increase to outbreak proportions. Fol- 
lowing severe defoliation over large areas the infestation usually di- 
minishes owing to overpopulation and other natural control factors, 
and a period of years elapses before it builds up again, thus giving the 
trees an opportunity to recover. It frequently happens, however, “that 
the amount of foliage present is Just sufficient to maintain the popu- 
lation to maturity, in which case the trees may be completely defoli- 
ated, or nearly so, for two or more consecutive years. One complete 
defoliation will not kill thrifty hardwoods, but is fatal to the conifers. 
Repeated defoliation of hardwoods so reduces their vigor that see- 
ondary insects often contribute considerably to the mortality of the 
trees, especially during periods of deficient rainfall. 
The aesthetic value of the trees in parks and woodland recreational 
areas, along roadsides, and the shade and ornamental trees in residen- 
tial areas necessitates enormous expense each year for protection 
against this pest. 
“Natura, Enemirs.—Since 1905 many millions of parasites and 
predators of the gypsy moth have been imported from Europe and 
Japan. Of the many species imported, 15 are known to be established 
in New England, and about 10 of these are now of considerable im- 
