LIFE HISTORY AND HABITS. 30 
EFFECT OF TEMPERATURE ON THE ADULTS. 
The adults of many of the eastern species have been reported by 
some observers as being primarily nocturnal in habits.^ Other 
observers record them as flying readily both by day and night. The 
adults of Limonius californicus seem without exception to be warm- 
weather insects. They not only attain their greatest activity 
during the middle of the day when the heat and light are at the 
maximum, but during the morning and evening hours they are 
sluggish and quiet. Some specimens were kept in the writer's 
room during their entire life and none was ever observed feeding or 
copulating at night. On the warmest nights a very few were observed 
moving about sluggislily, but their activity at this time can not be 
compared to that which occurred during the daytime and especially 
when the temperature was over 75° F. 
Several experiments were conducted for determining the direct 
relation between temperature and activity. The apparatus used 
was very similar to that used in the boll weevil investigations,^ 
except that instead of the outer tube a flask was used, as it was believed 
that this would afford more even heating. 
The results agreed quite closely with those recorded in Bulletin 
No. 51 (pp. 101-102) and an approximation is given below: 
48° F. Beetles quiescent. 
54° F. Few crawling about sluggishly. 
60° F. Beetles all moving about. 
70° F. Beetles becoming active. 
75° F. More active, few flying. 
80° F. Many flying. 
85°-90° F. All flying, very active, seem greatly excited. 
93°-94° F. Period of greatest activity. 
97° F. Few becoming quieter. Seem to be suffering. 
99° F. Many becoming quieter. 
This experiment was varied slightly by placing damp filter paper 
in the inner tube so that the heat would not be so dry. The new 
results did not differ very startUngly from the preceding, except 
that the beetles did not seem to suffer so much at the higher tempera- 
ture and seemed less excited. 
Under field conditions 75° to 80° F. seems to be the optimum 
temperature for their various activities. At 70° F. they are quite 
active, but few are noted in flight, especially if there is a moderate 
wind blowing. At 60"^ F. very few are noted moving in the fields, 
and these are generally close around the* beets under which they have 
been hiding. The beetles are always more active on bright days 
than on darker days, even if the temperature is the same. This 
1 Comstock and Slingerland, Bui. 33, Cornell Agr. Exp. Sta., 1891. 
2 Bui. 51, Bur. Ent., U. S. Dept. Agr., PI. XVI, fig. 72, 1905. 
