In diving beetles, sperm forms massive “super-organisms” to reproduce
Mammals generally have evolved the same basic, boring way for males to fertilize an egg: just send a bunch of tiny individual sperm into the female reproductive organs. But in insects like the diving beetle, it gets way more insane.
The reproductive tracts of female diving beetles are like labyrinths, huge maze-like structures in which the male’s sperm can easily get lost. That’s why all the individual sperms come together as one giant conglomeration that can then navigate as a single entity, which increases the chances that they will navigate the reproductive organ successfully. Of course, in the case of diving beetles and other invertebrates, “success” doesn’t mean fertilization of the egg — typically, the female will simply take on the sperm and store it, sometimes for years, until she is ready to reproduce.