The most distinguishing character for identifying Simocephalus vetulus is the peculiar elongated shape of the eyespot. It is a common species widely distributed in Norway and also known as an early colonist of newly constructed ponds.
Simocephalus vetulus has a comparatively small head, noticeably delimited from the carapace by a depression on its dorsal side. Maximum height of the carapace is situated posterior to the middle. The most distinguishing character for S. vetulus in which it differs from respectively S. expinosus and S. serrulatus, is the peculiar elongated shape of the eyespot. This may be less evident in very young individuals. S. vetulus is more transparent than the two other species of this genus.
Female: Length 1.3–3.8 mm
Male: Length 1.1–1.3 mm
Ecology and distribution
S. vetulus is a littoral species which is widely distributed in Norway and found in more than 13 % of the water bodies. It is known as an early colonist of newly constructed ponds or after disturbances in established water bodies. It is much more common below 500 m a.s.l. than above. Though it is rare above 1000 m a.s.l., it is found as high as 1253 m a.s.l. The highest frequency of S. vetulus is found in small ponds and ditches. It occurs most commonly in near neutral water and is rare in acid water. The conductivity varies between 0.7–84 mS/m.
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