Species of Mesaphorura are very small (typically 0.7 mm in length) soil-dwelling Collembola. Until relatively recently, most Mesaphorura have been recorded under the name Mesaphorura krausbaueri but following work by Rusek and others, it is clear that there are several species 'hiding' under this name. According to Fjellberg (1998), Mesaphorura yosiii is a species of acid soils and this would agree with its only known localities in England which are heathland (literature records) and a single confirmed locality in conifer humus at Morden Bog (the slide in the NHML collection is labelled 'Mesaphorura krausbaueri' but the specimen is definitely Mesaphorura yosiii).
     The PSO formula of Mesaphorura yosiii is 11/011/10011. Other diagnostic characters include five setae in tibiotarsal 'B' ring, seta a2 present on th3, distance between p1 setae on abd4 greater than the distance between the p2 setae (Fig. 1), seta m0 on abd4 absent, 3+3 short setae on abd5 between the long a4 setae (Fig. 2), and anal setae l2' present.

Back to main page

Fig. 2 (above): Dorsal side of the fifth (abd5) and sixth (abd6) abdominal segments of the same specimen of Mesaphorura yosiii shown in Fig. 1. There are 3 short setae on each side (a1, a2, a3) between the midline and the long a4 setae.

Fig. 1 (above): Dorsal side of the fourth (abd4) abdominal segment of Mesaphorura yosiii collected from Morden Bog, Dorset in November 1963 by Peter Lawrence. The distance between the p1 setae is longer than the distance between the p2 setae. PSO, pseudocellus.