Folsomia manolachei is a common and widespread species. There has been some controversy over the legitimacy of separating this species from Folsomia quadrioculata but it is clear that Folsomia manolachei is a good species (Folsomia nana is a junior synonym of Folsomia manolachei). It is pale to dark grey with 2+2 ocelli and reaches a maximum length of 1.0 mm. The ratio of the length of the longest setae at the tip of the abdomen/length of mucro is usually between 2.0 and 2.8 (Fig. 1) (rarely up to 3.8). The manubrium has 1+1 apical ventral (anterior) setae (Figs. 2, 3). The dens has 7 (rarely 8) ventral (anterior) setae and 3 dorsal (posterior) setae (two at the base of the dens and one in the middle). The PAO is narrow, constricted in the middle and is about the same length or slightly longer than the width of ant1. An important and very reliable character is the position of the sensillum in the posterior corner of the dorsal side of the second thoracic segment. In Folsomia manolachei, this sensillum is IN the posterior row of setae (Fig. 4). In Folsomia quadrioculata, this sensillum is NOT in the posterior row of setae and is displaced anteriorly.
     While working through the Folsomia material in the NHML collection, I discovered several misidentifications of Folsomia manolachei for Folsomia quadrioculata and vice versa. Many of the literature records for Folsomia quadrioculata must be for Folsomia manolachei which is clearly an under-recorded species. Both species are sometimes found together in the same site.
     In well-cleared specimens, the posterior pair of ocelli may be very difficult to see.

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Fig. 2 (above): Male genital plate (gp) of Folsomia manolachei collected from Chazey Heath, Reading in 1985 by M.N. Wetton.
Fig. 3 (below): as Fig. 2 but in a different plane of focus to show the furca with 1+1 apical ventral (anterior) setae (*) on the manubrium (ma). d, dens.

Fig. 1 (above): Folsomia manolachei collected from Brantwood, Coniston in April 1971 by Harold Gough. The ratio of the length of the longest setae at the tip of the abdomen (abd)/length of mucro (mu) is only about 2.5.

Fig. 4 (above): Same specimen of Folsomia manolachei shown in Figs. 2 and 3. The sensillum (arrow) in the posterior corner of the dorsal side of the second thoracic segment (th2) is IN the posterior row of setae.