The Life Hisfonj of the Birch Tiiigid 113 



Natural Enemies: Two predaceous insects, a little anthoeorid, 

 Anthocoris borealis, and the larvae of a laee-wing'ed-fiy, (Jhrijsopa 

 sp.. were observed feeding upon both n^nnphs and adults in the 

 field. Adults are also occasionally parasitized by a small red mite, 

 Trombidiurn 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 arc fairly 

 well 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 wdde. 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 much 

 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 long 

 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. ;-Avidth, .15 mm. 

 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 S^agre, (Plate V, Fig. /) : 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 ram.; width, .64 ram. General color, dark 

 brown. Length of .in5;tar, four to eight days. 



