Grand Teton National Park Report
In the majority of animals, most or all of both pre- and post-zygotic parental investment is contributed by the female of the species. Thus, the females and their ability to invest in offspring represent a limited resource, which must be procured by a male if he is to reproduce successfully. It is on this basis that sexual selection theory predicts that there will be intense competition among males for access to sexually receptive females.
Evans, Howard E.
"A Comparative Study of Mating Strategies in Two Species of Philanthus (Hymenoptera: Sphecidae),"
University of Wyoming National Park Service Research Center Annual Report: Vol. 3
, Article 7.
Available at: http://repository.uwyo.edu/uwnpsrc_reports/vol3/iss1/7