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.
Parasitoid wasp
Many parasitoid wasps use larval Lepidoptera as hosts, but some groups parasitize different host life stages (egg, larva or nymph, pupa, adult) of nearly all other orders of insects, especially Coleoptera, Diptera, Hemiptera and other Hymenoptera. Some attack arthropods other than insects: for instance, the Pompilidae specialise in catching spiders: these are quick and dangerous prey, often as large as the wasp itself, but the spider wasp is quicker, swiftly stinging her prey to immobilise it. Adult female wasps of most species oviposit into their hosts' bodies or eggs. Some also inject a mix of secretory products that paralyse the host or protect the egg from the host's immune system; these include polydnaviruses, ovarian proteins, and venom. If a polydnavirus is included, it infects the nuclei of host hemocytes and other cells, causing symptoms that benefit the parasite.