46 
SOME INSECTS INJURIOUS TO TRUCK CROPS. 
screen them out by washing the soil through cheese cloth. This was 
quite possible, but very slow, and while screening them out the writer 
observed the beetles floating on the surface of the water. This dis- 
covery suggested a very simple method of separating them. The 
soil was placed in a screen-wire box and washed in a pail of water. 
This broke up all lumps, and the beetles floating to the top were 
picked up with a pair of forceps. 
EMERGENCE FROM HIBERNATION, 
Artificial emergence. — In anticipation of the emergence of the 
hibernating beetles some experiments were conducted to determine 
the temperature at which they might be expected to appear and their 
actions when forced from their natural winter quarters. Beetles 
taken from frozen string-pegs were placed in lantern chimneys and 
beginning with 28° F. the temperature was gradually raised and the 
actions of the beetles noted. At 40° the antennae began to move 
slightly; between 40° and 50° the beetles moved about slowly and if 
disturbed would jump a short distance. Between 55° and 60° the 
beetles were quite active and crawled around in the lantern chimney. 
Their activity increased as the temperature was raised until 105° 
was reached, at which point they gradually became inactive again. 
Table V illustrates the effect of temperature upon the beetles, begin- 
ning with that of the room and increasing to 146°. In this experi- 
ment the beetles were confined in a double tube with an air space be- 
tween and the temperature was raised gradually. 
Table V. — Emergence and activity of the hop flea-beetle in artificial temperatures. 
Date. 
1909, 
Marchl2 
March 1 
Do 
Do 
Do 
April 12 
Do 
Do..... 
Number 
Room 
Tempera- 
ture re- 
duced 
to— 
of in- 
sects. 
tempera- 
ture. 
°F. 
°F. 
10 
56 
56 
10 
56 
56 
8 
56 
56 
10 
56 
56 
10 
58 
58 
10 
56 
56 
10 
56 
56 
10 
57 
57 
i 
Greatest 
First 
activity | dead ftt _ 
°F. 
90 
90-100 
90-100 
98-100 
90-100 
60-70 
80-90 
°F. 
82 
90 
110 
114 
95 
78 
90 
110 
Last 
dead at- 
Time of 
experi- 
ment. 
°F. 
110 
146 
126 
138 
139 
110 
148 
Minutes. 
15 
15 
10 
20 
20 
5 
25 
When beetles were thawed out they all became active between 40° 
and 45° F. When the higher temperatures were reached, however, 
there was a considerable difference in their susceptibilities to the 
change as may be seen by referring to Table V. Some of the beetles 
which were forced from hibernation were placed, on January 27, in a 
cage containing a young nettle plant. On February 8 several holes 
