REPRODUCTIVE BEHAVIOR OF 
CLAEODERES BIVITTATA 
(COLEOPTERA: BRENTIDAE)* 
By Leslie K. Johnson 
Department of Zoology 
The University of Iowa 
Iowa City, Iowa 52242 
Promiscuous aggregations of adult brentid weevils often occur on 
host trees, where females gather to oviposit (Meads 1976; Johnson 
1982). In such a circumstance, in which a male can potentially 
inseminate many females, intense competition by males for females 
typically occurs (cf. Thornhill 1976; Alexander and Borgia 1979; 
Fincke 1982). In addition, members of the family Brentidae show 
considerable intraspecific variation in adult size (Sharp 1895; Soares 
1970; Damoiseau 1967). From the numerous studies that show that 
larger body size enhances competitive aggressive success (e.g. John- 
son and Hubbell 1974; Hamilton et al. 1976; Heinrich and Bartho- 
lomew 1979), it might be predicted that larger male brentids would 
enjoy greater mating success in breeding aggregations, and — 
provided that male size is an important competitive characteristic — 
that variation in male mating success would be commensurate with 
variation in male body size. I tested these predictions on an aggrega- 
tion of C/aeoderes bivittata Kirsch. (Coleoptera: Brentidae) in 
which the adults varied more than ten-fold in body weight. 
The results of the present study support the idea that body size is 
an important trait. Males of nearly equal size engaged in a ritualized 
contest which appeared to permit sensitive assessment of relative 
size, and larger males enjoyed greater success in fights over females. 
However, small ( 1 1-22 mm) as well as large males (31-39 mm long) 
were disproportionately represented in mating. Small males had 
greater than expected success partly because they at times took 
shelter under, rather than guarded, their females, emerging for cop- 
ulation when a larger rival was not present. 
* Manuscript received hy the editor December 12, 1982 
135 
