2l6 
Psyche 
[December 
are common in the area, this particular plant was the only one found 
supporting a fair population of lace bugs continuously. Actually, 
after collecting more or less intensively there for five summers, I have 
discovered C. mollicula on only one or two other willow clumps 
located about 150 yards west of the chosen station. Although I col- 
lected this species in the area on several occasions, they were never 
sufficiently numerous on any other willow to serve my purpose. 
Secondly, of the five tingid species that I have studied in this 
manner and others noted in the literature, C. mollicula has the 
shortest period of seasonal activity. Most of them disappear from the 
Salix by mid-August or even late July (note Figure V for i960 
season). C. pergandei Heidemann and other species may be collected 
on their respective hosts until late September or even into early 
October in favorable years. So far I have been unable to account for 
this. If C. mollicula hibernate early, I have yet to locate them. If 
they migrate to other willows (or another host species) , I have yet 
to find the evidence. In 1958 ten adults were taken on their host on 
May nth and a single specimen was found on September 7th, al- 
though none had been seen since August 3rd. 
Since the figures are largely self-explanatory, comment will be 
minimal. Overwintering adults emerge from hibernation as soon as 
leaf development favors feeding. Usually by mid-May temperatures 
have made this possible. However, in some years (1957 graph) the 
peak may not occur until June. Graphs for the three years plainly 
reveal seasonal differences that largely reflect weather conditions. 
Maturation of the annual brood may show a peak as early as mid- 
June (i960 graph) ... or possibly early July is more usual. From 
then on the number of adults taken tends to decline, often some- 
what irregularly, until by early August (or early September at the 
latest) no more are found. Since eggs are laid over a period of several 
Explanation of Figures III, IV, and V 
These figures present graphically the population trends for Corythucha 
mollicula Osborn and Drake for each of the years specified. The curves are 
based on the actual numbers (indicated on the left) of adult lace bugs col- 
lected on the dates given below. The uppermost curve represents the totals of 
all population samples for the season. Differences in the seasonal distribution 
of females and of males in these same collections are shown by the middle and 
the lowermost graphs respectively. 
Hibernating adults emerge from early to late May depending on the 
weather and temperature which also largely determine host plant leaf 
development. Maturation of the annual brood begins by early or . . . perhaps 
more commonly ... by late June, depending on the same environmental con- 
ditions. By late July or, apparently less frequently, by early September 
(Figure IV) the host plant has been deserted for the year. 
