_ 6 - 
44 from one peanut plant. As late as September 6, 1937, 226 beetles were 
collected from one cocklebur, 188 from one velvetbean plant, and 30 from 
one cotton plant. 
In July 1938 thousands of adults were collected for experimental 
purposes from cockleburs located around the borders of infested fields 
and during August from beneath velvetbean vines. It was common to find 
from 25 to 100 beetles per cocklebur and from 50 to 200 per velvetbean. In 
1938 the number of adults emerging was determined in three fields by the use 
of cages. The average emergence in these fields was 22.2, 23.5, and 110.5 
beetles per square yard. 
The seasonal decrease in the abundance of adults was observed during 
the fall of 1937 and 1938 by making daily counts of the number trapped in 
designated sections of a barrier surrounding infested fields. The decrease 
was much more rapid in 1938 than in 1937. During the period of September 
24-28, 1937, a total of 849 beetles were caught. The number captured de- 
creased to 136 for the period of October 14-18, and to 87 for the period of 
November 3-7. During the period of July 16-20, 1938, a total of 12,866 
beetles were caught. The number captured decreased to 1,600 for the period 
August 5-9, and to 9 for the period September 24-28. Only 3 beetles were 
captured during the period of October 14-18, and 5 during the period November 
3-7. The last beetle captured in the sections of the barriers under observa- 
tion in 1937 was taken on December 5 and in 1938 on November 21; however, 
living beetles were found as late as December 18, 1937, and December 7, 1938. 
Life-history studies 
The beetles used for life-history studies in 1937 were reared from 
pupae in the insectary or taken from pupal cells in the soil after trans- 
formation to adults, but those used in 1938 were secured from field emergence 
cages, outdoor rearing cylinders, or from their pupal cells in the ground 
after transformation to adults. Beetles reared under insectary conditions 
from egg to adult, or from the larval or pupal stage to adult, are not so 
vigorous as those reared under outside conditions. In 1938 beetles were 
taken on the date of their emergence and confined exclusively to a certain 
plant foliage so that the effect of the various foods on the length of the 
different periods in the life and on the fecundity of the beetle might be 
studied. The plants utilized in these studies in 1938 were peanut ( Arachis 
hyp ogaea L. ) , upland cotton ( Gossypium h irsutum L.), strawberry ( Fragaria 
c hiloens is (L.) Duchesne), blackberry ( Rubus cuneifolius Pursh), pecan 
(Carya p ec an (Marsh.) Engl, and Graebn . ) , and a grass ( Paspalum panicu - 
latum L. ) . 
Preoviposition per iod. — The average preoviposition period for 32 
individuals in 1937 was 11.4 days; the periods ranged from 4 to 37 days. 
During the preoviposition period three of these beetles were fed on peanut 
foliage and 29 on cotton foliage. 
The preoviposition periods for beetles fed on various kinds of foliage 
in 1938 are shown in table 1. It is seen that different foods had some 
