Isotoma caerulea/viridis and Isotoma anglicana are very similar and can only be reliably separated (using slide-mounted specimens) by examining the manubrial 'teeth' and setae on the dens. Isotoma viridis has a single pair of 'teeth' on the thickened apical edge of the manubrium, whereas Isotoma anglicana/caerulea have two pairs of manubrial teeth. I. caerulea has 2 basal dorsal setae on the dens, I. anglicana has 3.
Isotoma caerulea, Isotoma viridis.
Confirmation requires microscopic proof of presence of two pairs of manubrial teeth.
All year round.
Widespread and fairly frequent in Britain.
Status in Leicestershire and Rutland not known.
Leicestershire & Rutland Map
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