Female cicada killer wasps, Sphecius speciosus, make nests in the ground. A single larva, feeding on large an insect prey provided by the mother develops in each nest. Around the nesting area, males perch and hover, fighting other males and watching for female wasps to emerge. Fighting involves colliding while flying, kicking and butting. Larger males can deliver more force and win the battle for territory.
John Alcock was able to show that the larger males can claim the best territory. He captured males patrolling the nesting area and weighed them. Those males were quickly replaced by nearby males. The replacements were then captured and weighed. The average weight of the original males claiming the territory was determined to be significantly larger than the weight of males that replaced them. This suggests the larger males are better able to defend a territory against their smaller rivals.
John Alcock. Male size and territoriality in the cicada killer wasp Sphecius speciosus. Journal of Natural History, Volume 50, 2016 – Issue 23-24.