Sminthurides aquaticus is a common species which is probably widely distributed (although there are no records from southwest England). It is yellow with some bluish pigment on the dorsal surface. Males reach 0.5 mm in length whereas females grow to 1.0 mm.
     In Sminthurides species, the male antenna is modified to grasp the female during mating and the long spine on the second antennal segment (ant2) is curved. Females do not possess sub-anal appendages (SAA). In Sminthurides aquaticus, the fourth antennal segment in the female is not divided into subsegments (Fig. 1). A tibiotarsal organ (tt organ) is present on the third leg (Fig. 2). The long seta of the tt organ does not bear a lamella (Figs. 2, 3). The empodium of the foot bears a long filament that reaches well beyond the tip of the claw (Fig. 3). The mucro is about half as broad as long and the ventral lamella is striated (Fig. 4).
     Sminthurides aquaticus is most frequently found on the surface of standing water.

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Fig. 1 (above): Fourth antennal segment (ant4) of a female specimen of Sminthurides aquaticus collected from Farnham, Surrey in April 1950 by F. Laing.

Figs. 2 (above) and 3 (below): Foot and tibiotarsus of Sminthurides aquaticus collected from Wisley in May 1966 by D.H. Murphy at two levels of magnification.

Fig. 4 (above): Mucro of the same specimen of Sminthurides aquaticus shown in Fig. 2.