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The Staphylinidae, rove beetles and related forms, is an absolutely massive array of insects. In fact, thanks to some relatively recent waves of the redefinition wand, the Staphylinidae is not only the largest recognised family of beetles but the largest family of animals of any kind. It even beats out the Curculionidae weevils that were the previous fore-runners. One might think that such a diverse group of animals would be the subject of extensive attention but that is simply not the case. I've commented before that part of the reason for this neglect is that staphylinids are a simply horrid group to work with but they still deserve a better look.
The original rove beetles belong to the tribe Staphylinini, a cosmopolitan group with more than 5300 known species and probably many more yet to be described. They are mostly active predators of other arthropods, hence the name 'rove beetle' in reference to their roving habits. One particularly large species (up to about three centimetres in length), Ocypus olens, has garnered the moniker of 'devil's coach-horse'. Several genera are found in association in ants and a termitophilous genus Sedolinus was recently described from South America (Solodovnikov 2006). The exact nature of its association with its termite hosts remains uncertain though it is worth noting that it shows less marked morphological adaptations than other termitophilous staphylinids. The South American Amblyopinus and closely related genera in South America and Australia are found amongst the fur of rodents and small marsupials. Because they are often attached to their host by the mandibles, they were long believed to be parasites feeding on blood or skin secretions. However, further studies found that they do not bite into the host but instead grip to its fur. And rather than feeding on the host itself, they feed on other, actually parasitic arthropods also present on the host (Ashe & Timm 1987).
The classification of Staphylinini is currently in the progress of going through a major shake-up. Not only were many of the taxa within the tribe previously poorly defined, what definition they had was mostly taken from Holarctic taxa. Species found in other parts of the world had largely been classified by finding what Holarctic taxon they most resembled, at least superficially, slotting them therein and then jumping on them until they could be made to fit. A prime example of this awkwardness revolves around the genus Quedius, to which species have been assigned from around the world. Molecular phylogenetic studies have found that a cosmopolitan Quedius represents a polyphyletic grouping (Brunke et al. 2016). Southern Hemisphere taxa assigned to Quedius or believed closely related are not only not immediate relatives of the true European Quedius, but they have been assigned to entirely distinct subtribes representing strongly divergent lineages in the Staphylinini.
REFERENCES
Ashe, J. S., & R. M. Timm. 1987. Predation by and activity patterns of 'parasitic' beetles of the genus Amblyopinus (Coleoptera: Staphylinidae). Journal of Zoology 212: 429–437.
Brunke, A. J., S. Chatzimanolis, H. Schillhammer & A. Solodovnikov. 2016. Early evolution of the hyperdiverse rove beetle tribe Staphylinini (Coleoptera: Staphylinidae: Staphylininae) and a revision of its higher classification. Cladistics 32 (4): 427–451.
Solodovnikov, A. 2006. Adult and larval descriptions of a new termitophilous genus of the tribe Staphylinini with two species from South America (Coleoptera: Staphylinidae). Proceedings of the Russian Entomological Society, St. Petersburg 77: 274–283.
Is it known roughly how old Staphylinidae and Staphylinini are?
ReplyDeleteThe Staphylinini go back at least to the early Cretaceous according to Brunke et al. (2016). The earliest fossil I've found referred to the Staphylinidae comes from the Late Triassic.
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