Elatherids are perfectly distinguished from all other coleopterans by a singular morphological peculiarity: they have a device (like a spring = that allows them to jump a few centimeters when they fall on their back or make the same energetic movement when captured by a predator
Sometimes, in entomology, to distinguish one species from another, you have to look at very particular and even subtle features. Some ants are distinguished by the number of antennal segments, while to distinguish the almost 7,000 different species of elatherids one must look at the hairiness and shape of the penis .
Genitalia and entomology
In fact, entomologists spend a lot of time looking at the genitalia of insects . Sometimes this is the most effective way to get to know an insect species. For example, what makes a new species of louse like Dennyus simberloffi special from its closest relatives is precisely that its genitalia are exceptionally small, and its head and anus are very wide.
The flea penis is the longest penis of all insects (in proportion). It has so many hooks, springs and prongs that, more than a penis, it looks like a Swiss utility knife.
The oldest known penis species is a hard-shelled marine creature called Colymbosathon ecplecticos. This Greek term means "amazing swimmer with a big penis."
Another particularly striking case is that of the insects of the genus Neotrogla, which are not an isolated case of reversed sex, but their females are the only ones characterized by having a penis .
The female inserts her erectile organ into the male to absorb sperm and other nutritive fluids.