Folsomides

Folsomides parvulus, copyright Brendan O’Loughlin.

Belongs within: Isotomidae.

Folsomides is a genus of isotomid springtails lacking anal spines and with reduced setation on the furcula (Christiansen & Bellinger 1980). The cosmopolitan species F. parvulus and F. centralis are among the most dominant springtails in tropical regions (Deharveng et al. 2020).

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 sp., copyright Donald Hobern.

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?

Systematics of Folsomides

Characters (from Christiansen & Bellinger 1980): Integument smooth. Fourth antennal segment lacking apical bulb. Postantennal organ present. Unguis toothless, unguiculus small and toothless, tenent hair short and acuminate. Abdominal segments usually sharply demarcated, sixth abdominal segment projected posteriorly. Anal spines absent. Ventral tube with 3+3 distal setae. Furcula with mucro more or less fused to dens, ventral manubrial setae absent, no more than three dorsal and one ventral dental setae present.

<==Folsomides Stach 1922 [incl. Subisotoma Stach 1947]CB80
|--*F. parvulus Stach 1922CB80 (see below for synonymy)
|--F. americanus Denis 1931CB80 (see below for synonymy)
|--F. angularis Axelson 1905CB80
|--F. anops Deharveng, Bedos & Lukić 2020DBL20
|--F. centralis (Denis 1931)DBL20
|--F. decemoculatus Mills 1935 [=Proisotoma decemoculata; incl. F. millsi Paclt 1945]CB80
|--F. deserticolaW74
|--F. loftyensisMC13
|--F. marchicus (Frenzel 1941) [=Proisotoma marchica]CB80
|--F. monosetis Massoud & Rapoport 1968DBL20
|--F. petiti (Delamare 1948)CB80
|--F. pseudoparvulus Marynova 1978DBL20
|--*Subisotoma’ pusilla Schäffer 1900CB80
|--F. semiparvulus Fjellberg 1993DBL20
|--F. teres Christiansen & Bellinger 1980CB80
|--F. whitteni Deharveng, Bedos & Lukić 2020DBL20
`--F. yucatanicus Kováč & Palacios-Vargas 1996DBL20

Folsomides americanus Denis 1931CB80 [=Proisotoma (Folsomides) americanaDBL20; incl. F. anophthalamis Hepburn & Woodring 1964CB80, F. stachi Folsom 1937DBL20]

*Folsomides parvulus Stach 1922CB80 [=Proisotoma (Folsomides) parvulaDBL20; incl. F. exiguus Folsom 1932DBL20, F. parvus Folsom 1937DBL20]

*Type species of generic name indicated

References

[CB80] Christiansen, K., & P. Bellinger. 1980. The Collembola of North America north of the Rio Grande: A taxonomic analysis vol. 2. Families Onychiuridae and Isotomidae. Grinnell College: Grinnell (Iowa).

[DBL20] 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.

[MC13] Majer, J. D., S. K. Callan, K. Edwards, N. R. Gunawardene & C. K. Taylor. 2013. Baseline survey of the terrestrial invertebrate fauna of Barrow Island. Records of the Western Australian Museum Supplement 83: 13–112.

[W74] Wallace, M. M. H. 1974. The entognathous hexapods. In: CSIRO. The Insects of Australia: A textbook for students and research workers. Supplement 1974 pp. 31–32.Melbourne University Press.

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