Injury (Fig. 45) : This tingid occurs on the yellow birch trees by the thousands and it is undoubtedly the most injurious leaf feeding insect upon the yellow birch tree in the vicinity of Cran berry Lake. Although large trees are frequently infested it seems to prefer the younger trees and seedlings. During the summers of 1917, 1918, 1919, and 1920 the insect has been especially abun dant in the vicinity of Barber Point. Numerous young birches were so badly infested that the leaves were almost entirely dis colored by its feeding punctures. Tn fact, the discolored leaves of badly infested trees by the last of July would attract one's attention several yards away. Later, many of these loaves would be almost entirely destroyed. Ironwood probably ranks next to yellow birch as a preferred food-plant, but white birch and beech are often badly infested. Mountain ash and the various species of maples do not seem to attract the insect very frequently and never in great numbers; in fact they are very rarely infested at all. There are two generations a year in the Adirondacks, the second generation hibernating as adults over the winter among the fallen leaves on the ground.
The adults and nymphs feed almost entirely on the under-side of the leaves (Fig. 45). The young nymphs, especially during the first and second instars, feed largely in colonies, but they gradually scatter during• the older stages. The discoloration, caused by the feeding of the insects, is very conspicuous on both sides of the leaves (Fig. 45). In addition to these discolored and feeding areas there are small blackish spots on the under-side of the leaves where the faeces have been deposited.
Natural Enemies: Two predaceous insects, a little anthocorid, Antlroco•is borealis, and the larvae of a lace-winged-fly, C/»..ysopd sp., were observed feeding upon both nymphs and adults in the field. Adults are also occasionally parasitized by a small red mite, Tromin•rum, sp., the latter usually being attached to the ventral side of the abdomen.
Eggs: The eggs are deposited on the under-side of the leaves in the axil of the veins. They are placed on end (only the base of each egg being slightly inserted in the tissue of the leaf) and in no definite order, but usually in groups ranging from four to ten eggs each. Sometimes only one and at other times about a dozen or more eggs are laid in a single group. The eggs are fairly welI concealed on yellow birch leaves by the pubescence along the veins of the leaves.
The egg (Plate V, Fig. c) is sub-elliptical, slightly curved, about .6 mm. long and not quite one-third as wide. The cephalic end is somewhat constricted and closed by a cap or lid. The color varies from brown to a very dark brown, but the cap is always mitch lighter and of a grayish color. They hatch about ten days after deposition.
First Nymphal Stage (Plate V, Fig. d) : Much more cylin drical elongate, and thicker than in the other instars. Antennae composed of three segments, the third long and with a few Iong setae. Head with five tubercles, the anterior pair with a single spine on each, the median and the posterior pair with two spines on each. Abdominal segments two, three, four, five, six, seven, eight and nine with a small tubercle, bearing a slender spine, on each side. Both pro- and mesothorax armed on each side with a spine. Abdominal segments two and eight bearing 'a pair of small dorsal tubercles with a spine on each segments five and six with large and prominent dorsal tubercles, each tubercle bearing three slender spines. Mesothorax also with a dorsal pair of tubercles, each bearing a slender spine. Length, .61 mm.;-width, .15 min. At time of hatching the nymph is almost colorless. Fully matured specimens are of a rather dark brown color. This instar lasts from four to six days.
Second Nymphal Stage (Plate V. Fig. e): Body broader in proportion to its length than in the preceding instar. The tubercles on the head are a little larger. The spines along the margin of the abdomen are stronger and larger and the spicules are more numerous over the entire body. Length, .75 mm. ; width, .43 mm. Color, dark brown. The length of this instar varies from five to ten days.
Third Nymphal Stage,(Plate V, Fig. f) : Antennae with four segments. The pro- and mesothorax larger and the entire insect more oval in outline. A few small spines have appeared on the tubercles. Length, 1.01. mm. ; width, .64 mm. General color, dark brown. Length of •instar, four to eight days.
114 New York, Atote College of Forestry Fourth Nymphal Stage (Plate V, Fig. g) : Tubercles moder ately large, each bearing several spines. Prothorax considerably larger, the mesothoracie wing-pads quite prominent. Small spieules have appeared on the bases of large spines. Length, 1.68 mm.; width, .76 mm. General color, dark brown, the base of the abdomen with a lighter area. Length of instar, five to twelve clays.
Fifth Nymphal Stage (Plate V, Fig.: Tubercles on the head quite large and prominent, each bearing several spines. Tubercles and spines much larger. Spinules present as in the pre ceding instar. Prothorax very prominent, the median anterior portion considerably raised and inflated, mesothoraeie wing-pads very large, completely covering metathoraeie wing-pads and extending on the fourth abdominal segment. Spines on lateral margins of abdominal segments covered by wing-pads wanting. Length, 2.2 mm. ; width, 1.3 mm. The general color is dark brown. the yellowish areas on the prothorax, wing-pads and base of the abdomen have increased in size. Length of instar, eight to fifteen days.