certain species parasitize or prey on other insects; others have been found feeding in 
the seeds and cones of conifers. Adults of the genus Hippelates are attracted to the 
eyes of humans and of other animals, and are very annoying. Certain species are 
also reported to transmit yaws and pinkeye. Gaurax apicalis Malloch, Oscinella 
coxendix (Fitch), and Hippelates sp. have been reared from the leaders of eastern 
white pine infested by the white pine weevil (762). 
Family Agromyzidae 
Leafminer Flies 
These flies are very small and light or dark colored (449). The body covering 
ranges from sparse bristles to dense hairs. The larvae are plant feeders; some mine 
the cambium, but the majority mine the leaves. 
Larvae of the genus Phytobia feed in the cambium of living trees, making long, 
thin, gradually widening mines (fig. 215). These mines sometimes originate in the 
top of the tree and extend all the way to the base and into the roots. They cause 
defects known as pitch-ray flecks. Heavily infested logs may be rendered unfit for 
some uses. 
F-506078, 506069 
Figure 215.—Cambium miner work: left, streaklike, 
longitudinal mines on trunk and roots of infested trees; 
right, pitch-ray flecks in the wood. 
Phytobia setosa (Loew), the red maple cambium borer, attacks red and sugar 
maples (523). Adults are small and dark colored. The larvae are opaque white and 
about 16 mm long. P. pruinosa (Coquillett) infests cherry, maple, and sweet and 
river birches. Adults are about 3 to 4 mm long; the larvae are up to 30 mm long. 
This species apparently lays its eggs in the forks of branches near the tops of trees 
and the larvae tunnel all the way down into the roots. P. amelanchieris (Greene), the 
amelanchier twig borer, attacks serviceberry, and P. pruni (Grossenbacher) at- 
tacks cherry. 
The native holly leafminer, Phyfomyza ilicicola Loew, 1s a serious pest of 
American holly in the Eastern United States. The adult is a small, grayish-black fly 
about 2.5 mm long. The female punctures leaves with her ovipostor and feeds on 
the juices exuding from the wounds. She also deposits eggs in the undersurfaces of 
leaves in punctures made near the midrib. The larvae mine the tissues between the 
leaf surfaces. The mine is hairlike at first but gradually widens as the larva 
continues to grow. Eventually it becomes blotchlike (fig. 216). Heavily infested 
leaves become unsightly and usually drop prematurely. Leaves damaged by feeding 
punctures become roughened, twisted, and stunted. The winter is spent as second 
449 
