Practically all of the more common orders of insects serve as hosts for the 
parasitic and predacious members of the Chalcidoidea, with the Lepidoptera, 
Diptera, Coleoptera, and Homoptera being preferred. The majority of the injurious 
tree-infesting species in this country are those that destroy the seeds of their hosts. 
Chalcids are mostly small to minute in size—some are less than 0.25 mm in 
length. The antenna is elbowed, the pronotum does not extend back to the tegula, 
the trochanter is two-jointed, the forewing is without either a stigma or closed cells, 
the ovipositor issues some distance before the apex of the abdomen, and a prepectus 
is present (697). 
Family Mymaridae 
Mymarids 
This family, closely related to the Eulophidae, is represented by more than 100 
species in the United States and Canada, the majority of which occur in the East. 
All members of the family are internal parasites in the eggs of other insects, 
particularly of Homoptera. Adults are mostly black or yellow and are extremely 
minute, usually less than | mm long. 
Polynema striaticorne Girault is an important parasite of several species of 
membracids. It also attacks various aphids and other insects. Its bionomics in Ohio 
and Illinois have been studied (52). Acmopolynema bifasciatipenne (Girault) para- 
sitizes the eggs of several species of tree crickets. Ooctonus aphrophorae Milliron 
attacks the Saratoga spittlebug (697). 
Family Trichogrammatidae 
Minute Egg Parasites 
The family Trichogrammatidae, with some 43 species, consists of extremely 
small insects all of which are internal parasites in the eggs of other insects (/5, 
697). Hosts have been recorded from the orders Lepidoptera, Coleoptera, 
Hymenoptera, Neuroptera, Diptera, and Hemiptera, but the Lepidoptera are pre- 
ferred. 
Trichogramma minutum Riley parasitizes the eggs of a great many species of 
insects, including many important enemies of trees. The following is a partial list of 
important eastern hosts: locust leafminer, gypsy moth, browntail moth, or 
angestriped oakworm, saddled prominent, walnut caterpillar, satin moth, hickory 
shuckworm, European pine shoot moth, Nantucket pine tip moth, forest tent 
caterpillar, spruce budworm (as many as 75 percent of spruce budworm eggs may 
be attacked), eastern blackheaded budworm, bagworm, elm sawfly, fall webworm, 
yellowheaded spruce sawfly, and fall cankerworm (974). 
The adult is less than 0.5 mm long, and females insert their eggs directly into 
host eggs in arboreal habitats. During warm weather, the life cycle may be 
completed within 9 to 16 days and there may be 12 or more generations per year. 
Family Eulophidae 
Eulophids 
Adults of this family are very small, ranging in length from | to 3 mm. Well over 
100 species are known to parasitize tree-infesting insects, several of which are 
important pests (974). A number of foreign species have been imported to the 
United States and Canada in efforts to suppress several species of introduced pests. 
The family contains more than 500 North American species (697). 
Chrysocharis laricinellae (Ratzeburg) (fig. 198), a parasite of the larch case- 
bearer and the birch leafminer, was introduced from Europe to New England and 
Canada in the late 1920’s and 1930’s. It is now widely established. Adults are bright 
metallic-green with pale-yellow legs, and are about 2 to 3 mm long. There may be 
three generations per year in the casebearer, but there is only one and a partial 
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