Sminthurinus species are very variable in colour pattern and it is essential to examine the presence or absence of ventral subapical setae on the dens in order to make a correct identification. The 'concolor-group' has TWO ventral subapical setae on the dens. (Figs. 1, 2). Sminthurus concolor is black-violet in colour and is found out of doors. Sminthurinus trinotatus is also found out of doors and is predominantly black with a prominent white spot on either side of the abdomen. Two other species have been recorded from glasshouses, or flower pots inside buildings. These are Sminthurinus domesticus (bluish-black all over, sometimes with a yellow median band) and Sminthurinus igniceps (body bluish-black, head white or pale yellow). However, the ease with which springtails can be imported on exotic plants means that the exact origin and identity of these specimens remains uncertain.
     Sminthurus trinotatus is a rare species for which there are only four records from England and Wales. The two confirmed localities (red dots) are a glasshouse in Bangor, North Wales (July 1925) and a flowerpot out of doors at the RSPB headquarters at Sandy, Bedfordshire (September 2001). Both these specimens have two ventral subapical setae on the dens and a prominent white spot on each side of the abdomen. The other two records (green dots) cannot be confirmed as the presence or absence of ventral subapical setae on the dens was not established.
     Sminthurinus trinotatus reaches 0.8 mm in length. The fourth antennal segment (ant4) is NOT subdivided. Both edges of the mucro are serrated. In females, the long setae surrounding the anus are expanded at the base and the sub-anal appendages (SAA) are feathery at the tips. The empodium of the second and third legs (leg2 and leg3) is slightly shorter than the claw, but is longer than the claw on leg1. The tenaculum (i.e. the 'catch' for the furca) has one seta. Apparently, Sminthurinus trinotatus is the only member of the 'concolor-group' with only one seta on the tenaculum.

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Fig. 1 (above) and 2 (right): Distal dens at two levels of focus of Sminthurinus trinotatus collected from a glasshouse at Bangor, North Wales in July 1925 (collector not known). There are two (1, 2) ventral subapical setae on the dens.