Female L. fabalis.
Goodwin & Fish (1977) wrote that the colour of the female’s ovipositor is “to varying degrees black pigmented” on L. obtusata, while that on L. fabalis “lacks pigmentation” in 99% of cases in Wales. Reid (1996) stated that it is not so in all areas.
This specimen has an ovipositor that is pigmentless (1) except for some black pigment at the anterior (2), so fits the description of L. obtusata, but the shell size, form and colour match those of males of L. fabalis (penes checked) found with it on Fucus serratus. No male L. obtusata were found on the shore, so this female is considered to be L. fabalis. In my (I.F.S) opinion, Reid was correct to question the reliability of ovipositor colour for differentiation of the two species.
Shell height 13.3 mm. Llŷn, North Wales. September 2016.
Full account at: 02 Differentiation L. obtusata/L. fabalis

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