Please refer to the following link for details on this group:
Melandryidae = Link 1
The species vary from 3.2–16 mm long. Both larvae and adults are probably not predacious but rather prefer to feed on vegetation, rotting wood and some fungi that occur in older wood.
The base of the prothorax is usually narrower than the combined elytral bases, or much narrower than the combined elytral bases. The greatest prothoracic width is not narrower or only slightly narrower than the greatest elytral width, or distinctly narrower than greatest elytral width. These beetles have an elongated oval shape. There is no "neck" and their waist is either not present or barely visible. The top surfaces of body may be glabrous in some species. There are neither bristles nor setal scales present.
The species are not prognathous, and the eyes do not protrude. The variable sized filiform antennae have 10-11 segment and are not housed in a notch but they may have bristles. The scape is not swollen. Antennal insertions are either visible or not, but they are not hidden by lateral extensions of the frons. The mandibular prosthecae is well developed.
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Lawrence, J. F. 1991. Melandryidae (Tenebrionoidea) (=Serropalpidae). Pp. 505-508 in: Lawrence, J.F. (coordinator) Order Coleoptera, in: Stehr, F.W. (ed.) Immature insects, 2. Kendall/Hunt Publishing Company, Iowa, USA.
Löbl, I. & A.Smetana (eds). Lobl, I. & A. Smetana (eds.). 2008. Catalogue of Palearctic Coleoptera. Vol. 5: Tenebrionoidea. Apollo Books, Stenstrup, Denmark, p. 64
Nikitsky, N. B. & D. A. Pollock. 2010. 11.6. Melandryidae Leach, 1815. Pp. 520-533 in: Leschen, R.A.B.; Beutel, R.G.; Lawrence, J.F. (volume eds.) Coleoptera, beetles. Volume 2: Morphology and systematics (Elateroidea, Bostrichiformia, Cucujiformia partim). In: Kristensen, N.P. & Beutel, R.G. (eds.) Handbook of zoology. A natural history of the phyla of the animal kingdom. Volume IV. Arthropoda: Insecta. Part 38. Berlin, New York: Walter de Gruyter.
Watson, L. & M. J. Dallwitz. 2003+ . British insects: the families of Coleoptera. Version: 1st December 2010.