INSECT ENEMIES OF EASTERN FORESTS 619 
Polynema straticorne Gir. is a parasite of the buffalo tree hopper 
(Ceresa bubalus). This host is known best as a pest of apple, but 
conspicuous damage is also done to willow, cottonwood, maple, and 
elm. Balduf (78) published on the host and the parasite in Hlinois 
and Ohio. The adult is from 1 to 1.6 mm. long, reddish black to 
brown, with an elongate slender body. Females oviposit directly in 
host eggs. Development is completed as an internal parasite, and 
the adults emerge by cutting out a small hole in the chorion. Three 
generations develop during a year. The winter is spent as a larva, 
and the first adults appear in May. About 31 percent of the eggs of 
C. bubalus examined by Balduf were parasitized by P. straticorne. 
PHYTOPHAGOUS CHALCID-FLIES 
Many families of chalcid-flies contain species that are phytophagous. 
The family Agaonidae is composed of remarkable insects that live 
within figs and fertilize them, but it is represented by only a few 
species in the United States. Gahan (179) listed the phytophagous 
chalcidoids, except the fig insects. The principal phytophagous forms 
in the United States are found in the family Callimomidae, which 
contains a number of seed-infesting species, and the family Eurytomi- 
dae, which contains some seed-infesting species, but many more that 
infest grains and grasses, often forming galls or swellings on the 
stems. Although chalcidoid gall makers are sometimes injurious to 
trees in other parts of the world, the phytophagous forms that cause 
serious damage to the forest trees in this country are the seed-infesting 
species. Most of them belong to the genus J/egastigmus, and most 
of them attack the seeds of coniferous trees. 
These seed chaleids are of economic importance. In certain local- 
ities a considerable proportion of the seed crop of a tree species may 
be destroyed in some seasons. This destruction not only seriously 
affects natural reproduction but is also an important factor in seed 
collecting, since a high percentage of cleaned commercial seed is often 
found to have been ruined by these insects. 
The life history of all the seed chalcids, so far as known, is essen- 
tially the same. The egg is laid in the seed late in the spring or early 
inthesummer. The larva completes feeding and hibernates. Trans- 
formation to adult takes place early in the spring, and the adults 
emerge by cutting a smooth round hole in the seed coat. Some larvae 
hold over and emerge the second or third year, and frequently as 
many as 50 percent of the brood may fail to emerge the first summer. 
Undoubtedly this is an important adaptation in the hfe cycle. The 
intermittent character of seed production of conifers is well known, 
and is apt to be common in other species. The seed chalcids attack- 
ing conifers emerge early enough to oviposit when the young cones 
have soft scales and the seed coats are unhardened (fig. 790). At this 
time the interior of the seed is occupied by a milky or Jellylike 
substance. 
The adult seed chalcids are almost always black with yellowish 
markings, are from about 14 to 14 inch long, and possess strongly 
exserted ovipositors, usually about as long as their bodies. Our more 
important species occur on the western coast and were listed by Keen 
eae Seed chalcids are reported to have killed 50 percent of the 
ouglas-fir seed crop at Ashland, Oreg., in 1913, although in most 
