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Psyche 
[December 
minimum. Since the mating female bears much of the male’s weight, 
a dwarfed male may be more fit in two additional contexts: 
1) By allowing the female greater activity, the rate at which 
additional females are encountered is increased. A potentially 
polygynous male can search for mates while in copulo (blocking the 
female genitalia until the opportunity for another copulation arises). 
Mating durations in D. veliei are shorter when unmated females are 
present (Sivinski 1977). 2) By relieving the female’s copulatory 
burden resources could be invested in ova the consort might 
fertilize. The longer the pairing the more likely this circumstance. 
Summary 
Intrasexual combats, while common in the Orthopteroidea, have 
apparently not been previously recorded in the Phasmatodea. 
Fights between males in Diapheromera veliei and D. covilleae are 
described. The minimal sexual size-dimorphism of the two species in 
comparison to other walkingsticks may be due to a high level of 
intrasexual competition brought about by atypical population 
parameters (high density, male-biased sex ratios). It is suggested 
that extreme dimorphism in the order relieves the burden an 
attached male places upon female resources during lengthy copula- 
tions. 
Acknowledgements 
I would like to thank Randy Thornhill, James Lloyd, Thomas 
Walker, Bruce Woodward, and Pat Sivinski for their numerous 
criticisms and suggestions which led invariably to improvements. I 
am grateful to Joan Martin and Susan Wineriter for the illustra- 
tions. 
References 
Alexander, R. D. 
1964. The evolution of mating behavior in arthropods. Insect Reproduction 
Symposium No. 2, Roy. Ent. Soc. Lond. 78-94. 
Balfour, H. 
1915. Note on a new kind of fishhook from Goodenough Island d’entrecas- 
teaux group New Guinea. Man. 15 : 171. 
