LIFE HISTORY While field observations have been limited to the summer months and are, of course, without ocular evidence con ditions during the winter months, the fact that the active part of its life cycle is practically completed between June 1 and Sep tember 1 makes it possible to detail the life cycle with entire confidence. The remainder of the year from egg deposition in late summer till egg hatching in late May must be passed in the egg stage within the twigs of birch. The earliest date of egg hatching is not known, but Dr. Drake has observed very young nymphs, evidently first instars, as early as May 30 and nymphs of third or fourth instar are found by July 1. The earliest adult female noted in 1920 was July 13 and the first male July 16. So we may conclude that the period of development from egg to adult is close to six or seven weeks. The rate of growth is not entirely uniform or else the eggs of different clusters hatch at different times as nymphs of many sires and different instars have been noted during the first two weeks of July with stragglers as late as the first week in August and adults have been emerging from July 13 to as late as the 29th. Adult females appeared July 16, but mating activity was not noted until July 23.
Emergence of adults from nymph ease appears to come in the early morning, such emergence being noted from the 17th to the 19th and between eight and ten. One individual, a male, which was followed most closely, had split the nymph case along thr dorsal line of head and prothorax when observed at a little before eight o'clock in the morning. It was attached to the underside of the petiole of a leaf with the head toward the tip of the leaf and in a position with reference to the twig which would place it nearly head downward, attachment to petiole being entirely by the tarsi of the nymphal ease. The head, pronotum and base of abdomen were exposed, as also the forelegs. and the wings were out but scarcely longer than the wing pads, their tips being folded under. The pronotum was no longer than in the last instar nymph and (lid not expand until after expansion of the wings. In this eoudil ion the insect remained fairly quiet for a time, as if resting after the initial effort, of exclusion. The color at this period was pinkish, wings and pronotum first appearing colorless, with expan sion later darkening to normal dark brown color. At nearly 7: 55
the insect became active, grasping the petiole with its forelegs and the nymph case with hind feet., withdrawing the abdomen from the case and turning at right angles to the deserted skin. Mean while the elytra and wings were expanding rapidly enlarging at base to full width and unrolling toward tip, the extreme tip being the last to lose its pink color and to acquire the natural symmetry of the adult elytron. At eight the elytra and wings were fully expanded and the pronotal expansion started and five minutes later the wings were fully out in nearly natural position and the pronotum partially expanded at base and tip, with a distinct. con striction near the tip. At S :08 faint indication on spots on head and base of pronotum could be seen. the coloration lying toward the head end but the elytra at this time was entirely transparent. At 8:10 the pronotum was nearly expanded, the base and tip nearly normal, but deeply hollowed at the middle and the tip reaching only to the tip of the abdomen, the following two minutes marking the beginning of coloration of the base of the elytra, the further extension of pronotum which is still constricted somewhat midway and nearly colorless. At 8: 15 the constriction of the was nearly gone and a minute later entirely so, the structure reaching its mature form and reaching nearly to the tip of the elytra, At this time the elytra nearly covered the wings, the latter at first drooping below, the elytra gradually drawing up closer to the body and assuming the position at rest. At 8: 20 the coloring became more noticeable, the costa darkening and the pronotiim becoming a. pinkish rod, the eyes dark red and all traces of the pronotal constriction are gone and thus the insect is fully normal except in color; and at 22 it walked about quite actively with apparently very free use of the legs which a few minutes earlier were flabby, helpless struetnres. The head has become bluish white; the further change noted in this specimen concerned simply the color, which at about 10 had become dark brown, the nearly normal hue for average specimens.