1. Trivia monacha. Top left to bottom right: 6.5mm juv., 10mm juv., 12mm juv., 10.2mm adult, 12 mm adult. LWS Scapa Flow, Orkney, all on 26th April 1975, except 12mm adult 7th Sept 1975. The last juvenile stage can be larger than the early adult stage.
2. Trivia monacha. Top left to bottom right: 6.5mm juv., 10mm juv., 12mm juv., 10.2mm adult, 12 mm adult. LWS Scapa Flow, Orkney, all on 26th April 1975, except 12mm adult 7th Sept 1975. The last juvenile stage can be larger than the early adult stage.

Trivia monacha. Top left to bottom right: 6.5mm juv., 10mm juv., 12mm juv., 10.2mm adult, 12 mm adult. LWS Scapa Flow, Orkney, all on 26th April 1975, except 12mm adult 7th Sept 1975. The last juvenile stage can be larger than the early adult stage.