The Folsomides fair
Published 21 February 2023
Springtail species can differ massively in their spread. Some can be found almost anywhere in the world; others seem restricted to incredibly specific locales. Within the cosmopolitan genus Folsomides, we may find examples of both.
Folsomides are small to moderate-sized springtails, ranging from less than half a millimetre to over a millimetre in length (Fjellberg 1993). Their habitus is supposed to be distinctive, with a slender, cylindrical body and a straight-backed profile that has a more or less sharp ‘break’ as the body narrows to the end of the abdomen. Coloration varies from completely white to bluish grey. Up to six ocelli are present on each side of the head.
Many species have an interstitial habitat, living buried in the soil. Others are found at surface level among moss or leaf litter. One species from the Canary Islands, Folsomides cumbrosus, is commonly found among epiphytic mosses growing on tree trunks (Fjellberg 1993). Pigmentation and eye development are commonly correlated with habitat; species found underground tend to have less pigmentation and few ocelli, as well as shorter appendages.
The soil-dwelling species Folsomides parvulus is among the most widespread of species, with records from Norway to Thailand, from Indiana to the Seychelles (Fjellberg 1993). In particular, it may be one of the most abundant springtail species in any tropical region. Conversely, two cave-dwelling species described from Vietnam by Deharveng et al. (2020) may have ludicrously restricted ranges. Folsomides whitteni was collected from only two caves, one of which has since been completely destroyed by mining. In the other, which has been significantly damaged by tourist traffic, it was only found in a single bat guano pile at the base of a chimney. Folsomides anops, the only species of the genus known to completely lack ocelli, was only found in the dark zone of a single littoral cave. Neither species was found in comparable samples taken near their respective sites. Both their sole known localities are threatened by further development and both species may be considered severely endangered. What else could you call something dependent on a single pile of dung?
References
Deharveng, L., A. Bedos & M. Lukić. 2020. The genus Folsomides in the Hòn Chông hills, Vietnam (Collembola: Isotomidae). Raffles Bulletin of Zoology Supplement 35: 32–47.
Fjellberg, A. 1993. Revision of European and North African Folsomides Stach with special emphasis on the Canarian fauna (Collembola: Isotomidae). Entomologica Scandinavica 23: 453–473.