/OO 
90 
30 
70 
eo\ 
so 
40 
30 
so 
/o 
NOTES ON THE BIOLOGY OF THE FOUR-SPOTTED BEAN 
WEEVIL, BRUCHUS QUADRIMACULATUS FAB . 1 
By A. O. Larson and Perez Simmons, Assistant Entomologists , Stored-Product Insect 
Investigations , Bureau of Entomology, United States Department of Agriculture 
This report summarizes a portion of the results of bean-weevil investi¬ 
gations which have been conducted for several years at Alhambra, Los 
Angeles County, Calif. The series of weevils from which the data dis¬ 
cussed in this paper were obtained consisted of 6i pairs of Bruchus 
quadrimaculatus Fab., including all the females and most of the 
males which developed 
from eggslaid August 15, 
1919. The prolonged de¬ 
velopmental period of the 
progeny of these weevils, 
extending as it did over 
the entire cool winter sea¬ 
son, made this series par¬ 
ticularly interesting and 
significant, and an analysis 
was made of the data from 
several points of view. 
The summary as presented 
deals with the effect of 
cool weather upon the de¬ 
velopment of the species; 
the effect of the age of the 
parent females, at the time 
of oviposition, upon the 
number and viability of 
the eggs and the develop¬ 
ment of the larvae; and 
the longevity, preoviposi- 
tion period, and egg laying 
of the parent insects. 
These data are all related 
to the rate of increase, and 
it is believed that they 
will contribute something toward a more thorough understanding of the 
life of this widespread and destructive species. 
The principal food of Bruchus quadrimaculatus in the bean warehouses 
of California is the blackeye cowpea or bean (Vigna sinensis ), which was 
used in the present experiment. Eggs were deposited from September 
18 to October 15 by females i which emerged September 17 to October 2, 
and the eggs of each female were counted and removed daily to shell vials. 
A survey of Table I at once suggests that the greatest number of eggs 
laid by a female is deposited during the early period of oviposition. 
Twenty-five laid their greatest number on the first day, 17 laid their 
greatest number on the second day, 7 on the third, 3 on the fourth, 3 on 
the fifth, and 6 laid the same maximum on two or more days. Figure 1 
shows, however, that the total number of eggs laid daily by all the females 
decreased with striking regularity as the females became older. Indi¬ 
vidual records of weevils Nos. 5, 9, 17, 49, 57, 58, and others, very nearly 
1 Accepted for publication Aug. n, 1923. 
17 
B 
a 
E" 
\ 
juS 
\ 
\ 
f 
s 
> 
/ 2343678 9 /O // /2 /3 /4 /S 
Fig. i—H atching of larvae and emergence of adult progeny from 
eggs laid by 61 Bruchus quadrimaculatus: Abscissas-“laying 
days: A, eggs laid each day: B, hatching of eggs: C, number 
of females ovipositing; D, emergence of adult progeny: E, 
percentage of eggs not producing adults. A t B, D, one cipher 
omitted and figures less than 10 shown as 1. 
(609) 
Journal of Agricultural Research, 
Washington, D. C. 
ahp 
Vol. XXVI, No. 12 
Dec. 22, 1923 
Key No. K-i2a 
