Folsomia penicula is widespread and moderately common. It is whitish spotted with black, has 2+2 ocelli (Fig. 1) and reaches 1.7 mm. The body setae are long; the ratio of the length of the longest setae at the tip of the abdomen/length of mucro is between 4.0 and 5.0. The manubrium has 4+4 (rarely 4+3) apical ventral (anterior) setae with 3+3 in a transverse row and 1+1 above (Fig. 2). The dens has 13-20 ventral (anterior) setae and 4 or 5 dorsal (posterior) setae. The PAO is narrow and is longer than the width of ant1 (Fig. 1). The ocelli may be difficult to resolve in cleared specimens (especially the posterior pair) and care should be taken not to confuse Folsomia penicula with the blind Folsomia spinosa.