The lesser stag beetle, Dorcus parallelipipedus male looks as a smaller version of the minor male of lucanus cervus cervus.
Obviously it always interesting to know what lucanidae species is the larvae that you found. However, because the larvae (particularly the smaller one) of all lucanidae look pretty much the same, it is very difficult to determine to which species the larvae belong to. This is particularly applicable for the dorcus parallelipipedus and lucanus cervus cervus, as the late L3 larvae of the DP could be as big as early to mid L3 larvae of the LCC. Considering the fact that DP is an abundant widespread species and normally live in the same areas as LCC this could be quite an issue. However, apparently it is still possible to identify the larvae of the common UK's lucanidae by comparing the shape of their last (terminal) segments. Here I came across the diagram published by T.E. Leiler in 1950 which could be useful:)
Leiler, T.E. (1950) Bestimmungstabelle der schwedischen Lucanidenlarven (Coleoptera). Opuscula Entomologica, 15, 157–160.
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