65 
that the re-stocking of the District of Columbia and its vicinity with 
the apparently exhausted supply of Southern forms was due mainly to 
flights induced by favoring winds, consists in the observed fact that 
there was not a corresponding increase in the numbers of Southern 
insects of other orders, such as beetles and bugs, insects of feeble 
powers of flight as compared to moths. The harlequin cabbage bug 
is an example of the less active fliers, as this insect was only slightly 
more abundant than in the previous year, until very late in the season, 
when injury occurred in some few localities. 
ATMOSPHERIC CONDITIONS DURING THE WINTER OF 1899 AND 1900 
AND SUBSEQUENTLY. 
The condition of the weather at different periods of the year was 
noted whenever it was thought that these conditions might affect 
insect life. Some of the more important phenomena should be men- 
tioned as a preliminary to remarks that will be made upon the effects 
of these conditions in limiting the increase or decrease of the insects 
under observation. 
No change worthy of mention which it was thought might affect 
insects injuriously was noted during the winter months of 1899. 
December 24 the temperature reached a maximum of 53° F. dur- 
ing the afternoon, and at this time several species of insects were 
observed at work in addition to those which will later be mentioned 
as affecting crucifers. That night, however, there was a considerable 
fall in temperature, a little more than 10° lower than the average for 
the day before, the minimum reaching 24°. 
During the next eleven days there was a considerable drop in the 
temperature, snow falling and the ground remaining frozen until 
January 6 or 7. At one time during this period the temperature 
descended to 9°. On the 5th the days began to become warmer, but 
the night temperatures continued quite low, as low as 15° on the date 
mentioned. 
February 24, after a protracted rainy speil of several days’ duration, 
the storm cleared, the sun came out, and the thermometer reached a 
maximum in the afternoon of 58° F. Search among grasses showed 
several forms of insects in activity near the surface, and it is proba- 
ble that many other insects were brought to the surface from their 
hibernating quarters by these conditions. That night a severe wind- 
storm with rain and snow came on, the temperature dropping by 6 
a. m. of the following day to 9° F., remaining below the freezing 
point for three days, but again attaining a maximum on March 1, of 
59°, similar to that experienced after the storm just specified. For 
the next twelve days the temperature was scarcely below the freezing 
point for more than a degree or two at any time until March 11, when 
4670—No. 30—OL 
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