(264FOfim) Folsomia fimetaria (Linnaeus, 1758)

Folsomia fimetaria is very common and widespread. It is white with 0+0 ocelli and reaches a maximum length of 1.4 mm. The ratio of the length of the longest setae at the tip of the abdomen/length of mucro is between 3.2 and 4.0. The manubrium has 4+4 apical ventral (anterior) setae with 3+3 in a transverse row and 1+1 above them (Fig. 1). The dens has 18-24 ventral (anterior) setae and 5 dorsal (posterior) setae. The PAO is narrow and is about the same length as the width of ant1.
Folsomia fimetaria has been found in soil, caves and flower pots and like Folsomia candida, is a popular laboratory test species. While working through the Folsomia material in the NHML collection, Steve Hopkin discovered several misidentifications of Folsomia fimetaria for Folsomia candida and vice versa. A good character for separating the species is that Folsomia candida has 2+2 or 3+3 setae on the ventral side of the third thoracic segment whereas these are absent in Folsomia fimetaria (see map for Folsomia candida for photo).

 

 

Fig. 1: Furca of Folsomia fimetaria collected from Alnmouth in March 1937 by Bagnall. The manubrium has 4+4 apical ventral (anterior) setae with 3+3 in a transverse row and 1+1 above them (*). d, dens.

 
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