To receive and store the spermatozoa until needed to fertilize the ova in insects.

Spermatheca of Earthworms(Pheretima posthuma),have two divisions namely Ampulla and diverticulum,which stores sperms and provide nutrition to them

A queen bee mates only once in her lifetime but it will usually be with anything up to about 20 drones. This takes place about a week after she emerges from the pupal cell. She stores the sperm in an organ called the spermatheca and this lasts for her entire laying life.

Bumble Bee queens over-winter from the previous year. In their mating (last year) they stored some of the sperm in a special organ called a spermatheca, from which they draw sperm as needed to make male offspring. Otherwise their offspring are worker females, who can only produce female offspring.

Female moths emerge from their cocoons with all their eggs fully formed in their abdomens, and the eggs are not fertilized until they are being laid (by male gametes stored in the female's spermatheca from mating). They keep laying eggs until they die in most cases. In other words, almost any female moth you find is a "pregnant moth", which is why there is no literature on behavior of pregnant moths.