The Bulletin 
97 
servations on the diurnal activities for bill bugs have been reduced to 
a curve representing the numbers of bill bugs active per acre. This 
curve does not take into consideration the number of bill bugs that 
were not active, as it was impossible to be absolutely sure whether 
you had actually secured all of the inactive bugs lying under clods and 
in similar situations. On the other hand, it was usually a compara¬ 
tively simple matter to determine the number of bugs which were feed¬ 
ing, laying eggs, or otherwise engaged in any of the daily activities of 
adult corn bill bugs. 
On the plat where most of the observations were made during the 
summer of 1912, 627 adult corn bill bugs of both sexes were found. 
This plat represented about one-third of an acre. Thus we have bill 
bugs occurring at the rate of more than 1,800 per acre. Yet in spite 
of this fact, the average rate per acre at the period of greatest activity, 
about 8 a. m., was usually not more than 1,200 per acre. Some other 
observations made in 1913 confirmed this general conclusion, that is, 
that even at the period of greatest activity only about two-thirds of 
the bill bugs in a given area would be actively engaged in feeding or 
egg laying. 
From an inspection of Fig. 62 it will be observed that on the average 
bright day in mid-season the two main periods of activity are from 
6 to 9 a. m. and from 4 to 8 p. m. The main periods of inactivity 
are from 10 a. m. to 3 p. m. and again from 10 p. m. to 3 a. m. 
Ordinarily on bright days no bill bugs will be found active from 11 
p. m. to after 2 a. m. The first bill bugs become active between 2 
and 3 a. m., these being joined by others between 3 and 4. a. m. 
So that on the average there are about 200 active bill bugs per 
acre by 4 a. m. Usually by 5 a, m. another 100 per acre have 
joined those already at work; by 6 a. m. the number of active 
bill bugs per acre has usually increased to 600, and by 7 o’clock 
this has usually doubled again; so that there are on the average about 
1,200 bill bugs per acre actively engaged in feeding and egg laying. 
By this time some of the earlier ones to become active have begun to 
seek shelter, but usually there are enough more becoming active, so 
that up to 8 o’clock the numbers are about constant. Very few new 
ones join the ranks after 8 o’clock, so that the numbers drop off rather 
rapidly, and late in the season, during late July and early August, on 
clear days when the sun is very hot in the corn-fields practically all of 
the bill bugs will be under cover by 11 a. m., where practically all will 
remain until about 2 p. m. In mid-season, mid-June to mid-July, the 
later arrivals in the morning w T ill linger through the warmer part of 
the day, so that it is not unusual to find bill bugs at the rate of 200 to 
300 per acre at this time of the day. 
Still earlier in the season, as from mid-May to mid-June, and on 
cloudy days later in the season, the bill bugs do not become very active 
until about 6 o’clock in the morning, but by this time there are usually 
