4 BULLETIN 1154, U. S. DEPARTMENT OF AGRICULTURE. 
MOVEMENTS OF THE BEETLES IN RELATION TO THEIR FOOD PLANTS. 
Moore and Cole 5 state that ''below 23° C. the beetles are generally 
inactive; 38-39° C. is optimum for their activity, while above 40° C, 
injurious effects are apparent. At 45° C. activity ceases quickly 
and permanently. Under the ruby light and in the dark most of 
the beetles become quiet." 
These observations are substantiated by the general increase in 
activity of the beetles during the day until 2 or 3 p. m., after which 
their activity decreases until dark, when flight ceases. The females 
deposit their eggs in the soil, and the egg-laying period extends over 
a period of from two to four weeks. In a large majority of cases the 
females enter the soil late in the afternoon and remain there until the 
following morning. During this time they deposit from 1 to 5 eggs. 
In cages females occasionally remained in the soil for 2, 3, or in some 
cases 4 days, although a large number of individuals usually spent 10 
to 15 hours out of the 24 hours in the soil, and during this time an 
average number of 3 eggs were laid. Nearly all the females under 
observation entered the soil late in the day, although in many cases 
eggs were laid only every third or fourth night. This is evidently 
what occurs under natural conditions, since numerous collections 
show that the proportion of females to males on the food plants is 
lowest between 7 p. m. and 7 a. m. Mating may occur several times 
each day throughout the egg-laying period. There is a distinct 
movement of the males toward those plants on which the females are 
feeding. On clear days, between 8 and 9 a. m., numerous males can 
be observed flying low over the ground in search of emerging females. 
During the early part of the day this tends to concentrate the beetles ' 
on low-growing plants such as smartweed, beans, and various weeds, j 
THE PROCESS OF INFESTATION. 
Mating and feeding more or less intermittently, there is a considerable 
movement of the beetles from plant to plant during the day. A 
female beetle on a plant will quickly attract many males, and, owing , 
to the gregarious nature of this species, other females as well. As 
has been stated, the males become active and are flying in the morning I 
before the maj ority of the females have emerged from the soil. During 
this period the male beetles feed erratically and for short periods on 
a large variety of plants. 
Later in the day, as the number of females in flight increases, the 
males usually select a plant on which one or more beetles are present. 
Between July 10 and July. 20 observations were made on five 2- 
year-old peach trees, 3 grapevines, 5 small sour cherry trees, 1 sassa- 
fras shrub, 5 plants of field corn, and 1 apple tree. Without dis- 
turbing the insects, the sex of the first 10 beetles to arrive on the j 
plants was noted. When the observations were begun, the plants 
were uninfested. After becoming infested, the plants on which \ 
these observations were made remained infested throughout the day, 
and the beetles included in the following data represent the first 10 
of an infestation which lasted at least one day: 
* Op. cit., p. 331. 
