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Springtail of the Month - 4

Species: Folsomia nana [Gisin 1957]
Family: Isotomidae
Collection site: From surface soil under garden holly hedge, by Tόllgren funnel. Mounts: Made in PVAL (polyvinyl lactophenol) Photomicrographs: Either scanned from colour prints or taken with an Olympus C2000Z digital camera and imaged processed in Paint Shop Pro (mainly cleaning up background!)


Folsomia nana is a small species. My specimens did not exceed 1.0 mm.Appears white to the naked eye, but on closer examination has sparse very small patches of dark pigment and four fairly obvious eye patches each with one eye. Noticeably long and thin compared with Isotomas and readily selected out of a collection in alcohol by the furca being held roughly at right angles to the long axis. Impossible to detect the fusion of abd 4-6 without close microscopical examination.


For family characters see S.O.T.M.3 (Tetracanthella), also an Isotomid. The genus Folsomia is distinguishable by complete fusion of Abd4-6, there being no intersegmental membranes or rings of cuticle devoid of setae to mark segment boundaries.


F.nana characteristics:

Furca fairly short ,just reaching into Abd 2 when folded. The posterior row of setae on Abd3 hardly reach the intersegmental boundary (but beware of intersegmental membrane stretching during mounting and flattening, which could make it mimic Gisin’s illustration of F. manolachei). Tenaculum with 4+4 teeth and 1 seta. Flattening can hide one or more teeth. Apart from differences in the length of the posterior row of setae on Abd3 Gisin used the length of the longest posterior abdominal setae compared with thelength of the mucro. His distinctions were as follows:F.quadrioculata (Tullberg) 1871 setae reach 3.5 to 5 times mucro length. The ratio for F.nana was 2.3 to 3.0 and for F.manolachei Bagnall 1939 2. Having measured only two of my specimens from micrographs my results were 2.6 and 2.7, so I identified them as F.nana. I can’t say I have great confidence in species separation on such characters, but I have immense admiration for Gisin’s work and keen observations.


The captions with the illustrations will, I hope be helpful.








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