Canadian Forest Service Publications
Diversity, classification and higher relationships of Mymarommatoidea (Hymenoptera). 2007. Gibson, G.A.P.; Read, J.; Huber, J.T. Journal of Hymenoptera Research 16:51-146.
Year: 2007
Issued by: Great Lakes Forestry Centre
Catalog ID: 34849
Language: English
Availability: PDF (request by e-mail)
Abstract
The superfamily Mymarommatoidea (Hymenoptera) has been referred to as ‘‘arguably the most enigmatic wasp taxon’’ (Vilhelmsen and Krogmann 2006, p. 290). Individuals are among the smallest of microhymenoptera, only about 0.3–0.8 mm in body length, but Mymarommatidae is one of the easiest families of Hymenoptera to recognize because of several highly distinctive features. Most conspicuously, the head has a hyperoccipital band of pleated membrane that enables the occipital region to expand and contract in a bellowslike manner, the forewing membrane has a mesh-like pattern, the hind wing is reduced to an apically bifurcate haltere-like structure, and the petiole is composed of two tubular segments (Gibson 1986, Gibson et al. 1999, Vilhelmsen and Krogmann 2006). Partly because of their minute size, mymarommatids are rarely collected and are poorly represented in most collections, but they have been captured on several subantarctic and Pacific islands (Valentine 1971, Beardsley et al. 2000) and on all continents north into Canada (Clouaˆ tre et al. 1989), Scandinavia (Hansen 1997) and far eastern Russia (Triapitsyn and Berezovskiy 2006). Specimens are also known in Dominican, Sicilian, Baltic, Canadian, Japanese, Taimyr, New Jersey, Burmese, French, Spanish and Lebanese amber, indicating the group has been present for at least 120 million years (Grimaldi and Engel 2005) and has long had a world distribution. Despite their long and apparently ubiquitous presence, almost nothing is known of their biology. Yoshimoto (1984) suggested that they are egg parasitoids, but the life stage they attack and their hosts remain to be discovered. A single individual was reared from a bracket fungus (Gibson 1993) and Huber (1987) noted that most specimens captured in the Northern Hemisphere had been collected in shady and relative moist areas such as deciduous forests. Clouaˆtre et al. (1989) did extract specimens from forest litter in eastern Canada, but they were also extracted from vegetation litter samples on three subantarctic islands (Valentine 1971). Based on sweep samples, Kryger (cited in Bakkendorf 1948, p. 216) suggested that mymarommatids are associated with low vegetation and remarked on their ‘‘very slow-moving gait — as an old man tired to death’’. Partly because of the lack of comprehensive comparative studies, Mymarommatidae has a complex nomenclatural history and uncertain phylogenetic relationships within Apocrita. Gibson (1986) and Vilhelmsen and Krogmann (2006) postulated several autapomorphies to support monophyly of the group, but these hypotheses and other character-state knowledge are based primarily on a single European species whose morphology has been studied in detail (Debauche 1948, Vilhelmsen and Krogmann 2006). Knowledge of other mymarommatid species and genera is limited largely to original descriptions. All 9 previously described extant species and 6 of the 10 extinct species are currently classified in Palaeomymar Meunier, 1901, which was established for a species in Baltic amber. Kozlov and Rasnitsyn (1979) stated that the diversity of the fossils they knew from the Cretaceous extended beyond the limits of a single genus, but that it did not seem possible to introduce any clear generic classification without an analysis of all accumulated material. Gibson et al. (1999) also suggested that the extant species could be classified in two genera based on differences in foretibial spur and forewing structure. The primary purpose of our study is to describe and illustrate the range of mor- 52