After the monograph on Leander squilla by Höglund (1943) in Sweden, any further work might seem repetitive; however, at Plymouth some differences in the biology of this species have been noticed, as might be expected from the different climates. It has been thought worth while to record these additional notes on the age and growth, together with records of the food.

De Man (1915) has separated the Scandinavian population as the forma typica from those of Holland, France and Britain, which he grouped into the variety intermedia, the only distinctive character being the length of the carpus of the second leg relative (either longer or shorter) to that of the chela. It is not known whether the two forms intergrade.