Wasp
Wasps first appeared in the fossil record in the Jurassic, and diversified into many surviving superfamilies by the Cretaceous. They are a successful and diverse group of insects with tens of thousands of described species; wasps have spread to all parts of the world except for the polar regions. The largest social wasp is the Asian giant hornet, at up to in length; among the largest solitary wasps is a group of species known as tarantula hawks, along with the giant scoliid of Indonesia ("Megascolia procer"). The smallest wasps are solitary chalcid wasps in the family Mymaridae, including the world's smallest known insect, with a body length of only , and the smallest known flying insect, only long.
Hystrichopsylla schefferi
Hystrichopsylla schefferi, also known as the mountain beaver flea and giant mountain beaver flea, is a parasitic holarctic insect belonging to the order Siphonaptera, the "siphon-wingless" (fleas). The fully grown adult can measure as much as in length, and it is the largest living flea in the world. It is native to the American Northwest. Though most members of the genus "Hystrichopsylla" are not strongly associated with any particular host animal and will generally parasitize insectivores and rodents, "H. schefferi" is monoxenously associated with the mountain beaver with which its range is coterminous. The fleas of the family Hystrichopsyllidae, along with the family Pulicidae, are the oldest of fleas in evolutionary history. "H. schefferi" can be distinguished from the very similar and closely related species "Hystrichopsylla gigas dippiei" by the number of spines in the pronotal comb, as "H. g. dippiei" has 36 and "H. schefferi" has 46.