MALE AGGRESSION AND FEMALE EGG SIZE 
IN A MATE-GUARDING AMBUSH BUG: 
ARE THEY RELATED?* 
By G. N. Dodson and L. D. Marshall 
Biology Department, University of New Mexico, 
Albuquerque, NM 87131 
Introduction 
The term “mate guarding” implies some form of active defense of 
a mate by the guarding individual. We previously described aspects 
of the mating system of Phvmata fasciata (Hemiptera: Phymatidae) 
including the first report of mate guarding for this family (Dodson 
and Marshall 1984). In the present report male P. fasciata aggressive 
behavior is described and found to be in accordance with the 
expectations of mate guarding. In addition, we relate female size to 
egg size and discuss how this relationship may play a role in the 
evolution of guarding behavior. 
Methods 
Ambush bugs were observed on prairie sunflower ( He/ianthus 
petiolaris ) in north central New Mexico. Because of low bug 
densities (see Dodson and Marshall 1984), encounters between 
single males and males guarding females were infrequent. Three 
naturally-occurring, guarding male:single male interactions were 
observed in 1982. In addition, 13 interactions were “manipulated” in 
the field to corroborate the accuracy of our natural observations. 
Manipulations involved transferring a single male to a flower 
already occupied by a mating pair. The transferred individual was 
placed as far from the pair as possible and then observed until it 
approached the pair or left the plant. Although there were some 
minor variations, three basic components of male:male interactions 
(see below) were the same for natural and manipulated cases. Most 
of the behaviors described here were also performed by bugs kept on 
plants in the lab. 
* Manuscript received hy the editor May 18, 1984. 
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