Macrothrix hirsuticornis is characterised by having a big compound eye and by the robust first pair of antennae. It is one of the most common species in Svalbard.
The dorsal edge of Macrothrix hirsuticornis forms a somewhat uneven smooth curve. It is more curved anteriorly to the relatively large compound eye than dorsally. Oscellus is placed near the tip of the rostrum. The first pair of antennae are robust, and anterliorly they have a needle attached close to their base. The two branches of the second pair of antennae are respectively three and four segmented, and much longer and thinner in other Macrothrix. It has a yellow-grey colour, sometimes with a greenish tinge.
Female: Length 0.5–2.0 mm
Male: Length 0.4–0.7 mm
Ecology and distribution
Macrothrix hirsuticornis is one of the most common species in Svalbard. On the mainland it is found in a few localities which are situated in northern Norway close to the Lofoten islands. G.O. Sars also found this species in the same area. All records are from the littoral of lakes (0.5–150 da) situated below 100 m a.s.l. pH is close to neutral, while conductivity is above 7.0 mS/m in the actual lakes. It may live close to the bottom sediment, in dense vegetation or in vegetation free areas, and is truly overlooked.
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