the early days of this century. T. nidicola quickly spread through- 
out the infested area. During recent years it has frequently para- 
sitized an average of 17 percent of overwintering brown-tail 
moth larvae. C. laxifrons also occurs throughout the infested 
area. Unfortunately, it parasitizes a very low percentage of the 
population. 
Chaetexorista javana B. & B., a native of Japan, was imported 
against the oriental moth in 1929 and 1930. As early as 1933, 
parasitism in the infested area around Boston, Massachusetts 
averaged 60 percent. Hrynniopsis rondanii Towns., a native of 
Europe, has been successfully introduced into California against 
the European elm leaf beetle. Colonies have also been liberated 
against the beetle along the Atlantic Seaboard but without success. 
Drino bohemica Mesn., a native of Europe, was successfully in- 
troduced into Canada against the European spruce sawfly during 
the thirties and forties. This is probably the same species that 
was introduced into the United States around 1906 as Sturmia 
inconspicua (Meig.) against the gypsy moth, brown-tail moth, and 
red-headed pine sawfly (205). It was recovered at gypsy moth 
colonization sites for several years thereafter, but it apparently 
did not become permanently established. It probably occurs now 
in northern Maine as a result of spread from New Brunswick and 
Quebec, where it appears to be one of the most effective parasites 
introduced against the European spruce sawfly. 
FAMILY OESTRIDAE 
WARBLES OR BOT FLIES 
Warble or bot flies are all parasitic on animals, and several are 
serious pests. They are best known as enemies of domestic ani- 
mals, but many species also attack various species of wild animals. 
The adults are medium- to large-sized flies and resemble small 
bees. Cephenomyia pratti Hunt. and C. phobifer (Clark) are 
serious enemies of deer. Various species of the genus Pseudo- 
bogeris infest squirrels, rabbits, cats, and meadow mice. Cattle 
are subject to serious infestations by the northern cattle grub, Hy- 
poderma bovis (L.) and the common cattle grub, H. lineatum 
(Villers). 
Order HYMENOPTERA 
The order Hymenopt:ra is one of the largest and most impor- 
tant orders of insects. Besides a large number of harmful species, 
the order contains a far greater number of beneficial species. 
Bees, wasps, and ants are among the better known groups. Bene- 
ficial forms include the well-known honeybee, plus a large number 
of less familiar forms. Most of the species are parasites of other 
insects, and many are important pollinators of plants. Among 
harmful species are the sawflies. Many of them are important 
pests of forest and shade trees and young trees in nurseries and 
plantations. 
The winged members of the order characteristically have four 
membranous wings, the front pair larger and more completely 
veined than the hind pair. The hindwings have a row of tiny 
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