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. Mesaphorura tenuisensillata is a very interesting case in point. The only slide labelled Mesaphorura tenuisensillata in the NHML collection is from the Isle of Mull identified by Rusek (the northern-most dot on the map). However, I have discovered several other specimens of this species labelled as Mesaphorura krausbaueri or Mesaphorura iowensis. Interestingly, these are all from high mountains in North Wales and Ireland. Thus Mesaphorura tenuisensillata would appear to be a species with a pronounced northern bias. It is possibly a glacial relic.
     The PSO formula of Mesaphorura tenuisensillata is 11/012/10011. There are two small anal spines (Fig. 1). Other diagnostic characters include six setae in tibiotarsal 'B' ring (Fig. 2), seta a2 absent from th3, distance between p1 setae on abd4 shorter than the distance between the p2 setae (Fig. 3), seta m0 on abd4 present (Fig. 3), 3+3 short setae on abd5 between the long a4 setae (Fig. 4), and anal setae l2' present.

Back to main page

Fig. 1 (above): Anal spines of Mesaphorura tenuisensillata collected from the summit of Tryfaen mountain, North Wales in September 1933 by May 1951 by W.M. Davies.

Fig. 2 (above): Foot of second leg of the same specimen of Mesaphorura tenuisensillata shown in Fig. 1. There are six setae in the 'B' ring of the tibiotarsus (1-6). Setae 3 and 5 (in parentheses) are on the underside of the tibiotarsus but are visible through the cuticle.

Fig. 4 (above): Dorsal side of the fifth abdominal segment of the same specimen of Mesaphorura tenuisensillata shown in Fig. 1. There are 3 short setae on each side (a1, a2, a3) between the midline and the long a4 setae.

Fig. 3 (above): Dorsal side of the fourth abdominal segment of the same specimen of Mesaphorura tenuisensillata shown in Fig. 1. The distance between the p1 setae is shorter than the distance between the p2 setae. Seta m0 is present. Ant, anterior; Post, posterior.