reach maturity. When this happens, the larvae usually vacate the trees and often 
migrate in search of food. When the food supply is depleted but not completely 
consumed before the larvae mature, many succeed in pupating but they are smaller 
than normal. This results in smaller than normal adults, and the number of eggs 
deposited per female is greatly reduced. Larvae seek sheltered places in which to 
pupate. Pupae may be found attached by silken threads to limbs and trunks of trees, 
stones, picnic tables, forest debris, buildings, vehicles, and the like. In heavy 
infestations, they are often found massed together in large numbers. The pupal 
stage lasts about 10 days or 2 weeks. 
The gypsy moth has long been considered one of the most important forest 
insects in the United States. Since the turn of the century, enormous sums of money 
have been expended by the Federal Government and the affected States to eradicate 
it, to suppress it, or to prevent its further spread (8/0). Despite these efforts, 
outbreaks have continued to occur in the older infested portions of New England 
often at 8- to 10-year intervals (/9), and have expanded to newer infested areas to 
the South and West (table 1). 
Defoliated trees show reduced growth and are more susceptible to attack by 
wood-boring insects and fungi than are undefoliated trees (249, 348, 608, 702, 
1245, 1246). Mortality of defoliated trees has been variable (/9/, 660, 702, 1156). 
Further losses result from the reduction in quality of forest sites in stands suffering 
repeated defoliations. Esthetic and recreational values are also reduced in outbreak 
areas. 
When the gypsy moth was introduced, the insect parasites, predators, and 
pathogens affecting it in its native habitats abroad were left behind, and it encoun- 
tered none in the Northeast that were capable of holding it in check. To remedy this 
situation, a program of importation of foreign parasites and predators was initiated 
in 1905 and has been continued intermittently to the present (252, 328, 613, 6/8, 
1014). Collections representing 45 different species of the parasites and predators 
were imported, colonies of which were released in infested stands in this country. 
Ten species of parasites and two predators became established (6/8, 1090). Two are 
hymenopterous egg parasites—Ooencyrtus kuvanae (Howard) and Anastatus dis- 
paris Ruschka; four are tachinid larval parasites—Compsilura concinnata 
(Meigen), Exorista larvarum (L.), Parasetigena silvestris (Robineau-Desvoidy), 
and Blepharipa pratensis (Meigen); two are hymenopterous larval parasites— 
Phobocampe disparis (Viereck) and Cotesia melanoscelus (Ratzeburg); two are 
hymenopterous pupal parasites—Monodontomerus aereus Walker and 
Brachymeria intermedia Nees; and two are coleopterous predators—Calosoma 
sycophanta (L.) and Carabus auratus L. 
One of the most important factors affecting heavy gypsy moth populations is the 
so-called wilt disease, caused by a nuclear-polyhedrosis virus. This pathogen 1s also 
a native of Europe. It may have entered this country in gypsy moth material 
imported for the recovery of parasites. During moth epidemics, it increases tremen- 
dously and decimates populations over large areas (3/2, 731, 990). Other natural 
control factors include low winter temperatures—exposed eggs begin dying at a 
temperature near — 28° C (48/, 1178). Small mammals devour large larvae and 
pupae found on the forest floor. Also, many larvae die of starvation in woodlands 
entirely stripped of foliage before the larvae reach maturity. Discussions of the 
population dynamics and ecology are available (/04, 187, 189, 726, 1106). 
Silvicultural practices designed to promote the health and vigor of stands are 
helpful in increasing tree resistance to gypsy moth damage (/05). A reduction in the 
231 
