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.
Polistes atrimandibularis
"P. atrimandibularis" is the smallest of the three social "Polistes" parasites. The size of the host’s species brood cells determines "P. atrimandibularis" size, with the smaller "P. atrimandibularis" emerging from the nests of "P. gallicus" and "P. associus". Likewise, the larger "P. atrimandibularis" emerge from the nests of "P. dominula" instead. This paper wasp has enlarged mandibles, used as weapons to injure hosts that resist parasite intrusion. They also have an enlarged first femur and a longer posterior tibia that is useful for when they must maintain a dominant position within the host colony.