To make sure their sperm fertilize the eggs, many male damselflies have a structure to scoop out the previous male's sperm from the female's spermatheca. Male migratory locusts plug the spermatheca opening so other males cannot deposit their sperm. Some male butterflies even coat the female's genitalia with a substance that hardens, preventing her from mating with other males. Male bed bugs avoid the issue altogether. They pierce the female's abdomen and inject sperm into her blood, sort of like taking a shortcut to her eggs.
Some insects are well-endowed by human standards.
The female mayflies have two genital openings, and the males have two penises. Others have a marathon endurance that humans can only envy. So, the next time you are lying in bed, wondering what is going on in the next room, wonder instead what the cockroaches in the kitchen are up to . . .