Ichneumonidae is a family within the insect order Hymenoptera. Insects in this family are commonly called ichneumon wasps. Less exact terms are ichneumon flies (they are not closely related to true flies), or scorpion wasps due to the extreme lengthening and curving of the abdomen (scorpions are not insects). Simply but ambiguously these insects are commonly called "ichneumons", which is also a term for the Egyptian Mongoose (Herpestes ichneumon); ichneumonids is often encountered as a less ambiguous alternative. Ichneumon wasps are important parasitoids of other insects. Common hosts are larvae and pupae of Coleoptera, Hymenoptera, and Lepidoptera.
There are over 60,000 species worldwide, and approximately 3,000 in North America - more than any other Hymenoptera family. The distribution of Ichneumonidae is one of the most notable exceptions to the common latitudinal gradient in species diversity because it shows greater speciation at high latitudes than at low latitudes.
Ichneumon wasps differ from the wasps that sting in defense (Aculeata
) in that the antennae have more segments; typically 16 or more, whereas the others have 13 or fewer. Their abdomen is characteristically very elongated, unlike in their relatives the braconids
. This lengthened section may also be segmented. Female ichneumon wasps frequently exhibit an ovipositor
longer than their body. Ovipositors and stingers
structures; some Ichneumons inject venom along with the egg, but they do not use the ovipositor as a stinger, per se
, except in the subfamily Ophioninae
. Stingers in aculeate Hymenoptera - which like Ichneumonidae belong to the Apocrita
- are used exclusively for defense; they cannot be used as egg-laying equipment. Males do not possess stingers or ovipositors in either lineage.
Some species of ichneumon wasps lay their eggs in the ground, but most inject them directly into a host's body, typically into a larva or pupa. Host information has been notably summed up by J.F. Aubert, J.F. Perkins, and H.T. Townes and coworkers.
In some of the largest species, namely from the genera Megarhyssa and Rhyssa, both sexes will wander over the surface of logs, and tree trunks, tapping with their antennae. Each sex does so for a different reason; females are 'listening' for wood boring larvae of the horntail wasps (hymenopteran family Siricidae) upon which to lay eggs, males are listening for emerging females with which to mate.
Upon sensing the vibrations emitted by a wood-boring host, the female wasp will drill her ovipositor into the substrate until it reaches the cavity wherein lies the host. She then injects an egg through the hollow tube into the body cavity. There the egg will hatch and the resulting larva will devour its host before emergence. How a female is able to drill with her ovipositor into solid wood is still somewhat of a mystery to science, though it has been found that there is metal (ionized manganese or zinc) in the extreme tip of some species' ovipositors.
Tapping with her antennae the wasp listens for the vibrations that indicate a host is present.
With the longer ovipositor, the wasp drills a hole through the bark.
The wasp inserts the ovipositor into the cavity which contains the host larva.
Depositing her eggs.
Depositing her eggs.
Taxonomy and systematics
The Ichneumonidae have been and still are quite a taxonomic
nightmare. About as diverse as the true weevils
), there are numerous small, inconspicuous and hard-to-identify ichneumon wasps. The sheer diversity means that DNA sequence
data is only available for a tiny fraction of the species, and that detailed cladistic
studies require major-scale computing capacity.
Consequently, the phylogeny and systematics of the ichneumon wasps are not definitely resolved. Several prominent authors - like H.T. Townes and J. Oehlke - have gone as far as to publish major reviews that defy the International Code of Zoological Nomenclature
Regardless, there exist a number of seminal works, including the extensive study and the synonymic catalogue by Townes but also treatments by other entomologists, namely J.F. Aubert who has a fine collection of ichneumon wasps in Lausanne.
The list presented here follows the suggestion of David Wahl of the American Entomological Institute
. It will be updated as necessary, as new research resolves the interrelationships of the ichneumonm wasps better and better.
The subfamilies are not listed in a taxonomic or phylogenetic sequence, as the relationships between the groups are not yet resolved to a degree to render any such arrangement even marginally reliable:
Famous ichneumonologists include:
- (1969): Les Ichneumonides ouest-palearctiques et leurs hotes 1. Pimplinae, Xoridinae, Acaenitinae ["The Western Palearctic ichneumon wasps and their hosts. 1. Pimplinae, Xoridinae, Acaenitinae"]. Laboratoire d'Evolution des Etres Organises, Paris. [in French]
- (1978): Les Ichneumonides ouest-palearctiques et leurs hotes 2. Banchinae et Suppl. aux Pimplinae ["The Western Palearctic ichneumon wasps and their hosts. 2. Banchinae and supplement to the Pimplinae"]. Laboratoire d'Evolution des Etres Organises, Paris & EDIFAT-OPIDA, Echauffour. [in French]
- (2000): Les ichneumonides oeust-palearctiques et leurs hotes. 3. Scolobatinae (=Ctenopelmatinae) et suppl. aux volumes precedents [The West Palaearctic ichneumonids and their hosts. 3. Scolobatinae (= Ctenopelmatinae) and supplements to preceding volumes]. Litterae Zoologicae 5: 1-310. [French with English abstract]
- (1976): The family-group names of the Ichneumonidae (excluding Ichneumoninae) (Hymenoptera). Systematic Entomology 1: 247-258.
- (1978): Further notes on family-group names of Ichneumonidae (Hymenoptera). Systematic Entomology 3: 245-247.
- (1976): The classification of the Anomaloninae (Hymenoptera: Ichneumonidae). Bulletin of the British Museum of Natural History (Entomology) 33: 1-135.
- (1966): Die westpaläarktische Arte der Tribus Poemeniini (Hymenoptera, Ichneumonidae) ["The Western Palearctic species of the tribe Poemeniini"]. Beiträge zur Entomologie 15: 881-892.
- (1967): Westpaläarktische Ichneumonidae 1, Ephialtinae. Hymenopterorum Catalogus (new edition) 2: 1-49.
- (1959): Ichneumonidae, key to subfamilies and Ichneumoninae – 1. Handbk Ident. Br. Insects 7(part 2ai): 1–116.
- (1960): Hymenoptera: Ichneumonoidea: Ichneumonidae, subfamilies Ichneumoninae 2, Alomyinae, Agriotypinae and Lycorininae. Handbk Ident. Br. Insects 7(part 2aii): 1–96.
- (1998): Explaining the latitudinal gradient anomaly in ichneumonid species richness: evidence from butterflies. Journal of Animal Ecology 67: 387-399
- (1969a): Genera of Ichneumonidae, Part 1 (Ephialtinae, Tryphoninae, Labiinae, Adelognathinae, Xoridinae, Agriotypinae). Memoirs of the American Entomological Institute 11: 1-300.
- (1969b): Genera of Ichneumonidae, Part 2 (Gelinae). Memoirs of the American Entomological Institute 12: 1-537.
- (1969c): Genera of Ichneumonidae, Part 3 (Lycorininae, Banchinae, Scolobatinae, Porizontinae). Memoirs of the American Entomological Institute 13: 1-307.
- (1971): Genera of Ichneumonidae, Part 4 (Cremastinae, Phrudinae, Tersilochinae, Ophioninae, Mesochorinae, Metopiinae, Anomalinae, Acaenitinae, Microleptinae, Orthopelmatinae, Collyriinae, Orthocentrinae, Diplazontinae). Memoirs of the American Entomological Institute 17: 1-372.
- (1965): Catalogue and Reclassification of Eastern Palearctic Ichneumonidae Memoirs of the American Entomological Institute 5: 1-661 pages.
- (1999): Classification and Systematics of the Ichneumonidae (Hymenoptera) Version of 1999-JUL-19. Retrieved 2008-JUN-18.
Taxonomy and Systematics