Mecinus janthinus group

Gosik, Rafal, Skuhrovec, Jiri, Caldara, Roberto & Tosevski, Ivo, 2020, Immature stages of Palearctic Mecinus species (Coleoptera, Curculionidae, Curculioninae): morphological characters diagnostic at genus and species levels, ZooKeys 939, pp. 87-165 : 87

Mecinus janthinus group

Differential diagnosis.

Larva. (1) body densely covered with asperities; (2) pedal lobes weakly isolated; (3) abdominal segment X reduced to three anal lobes of unequal size; (4) thoracic spiracle bicameral; (5) abdominal setae medium to very long, distinclty growing from abdominal segment I to VIII; (6) abdominal segments I-VIII with four pds and usually three ss; (7) head brown, flattened laterally; (8) frontal suture distinct; (9) endocarina 4/5 of the frons; (10) des4 usually shorter than des1; (11) presence of fs1; (12) absence of fs2; (13) fs3 as long as half of fs4; (14) head with two stemmata; (15) presence of cls1; (16) labial palpi two-segmented; (17) premental sclerite cup-like; (18) surface of postlabium densely covered with asperities.

Pupa. (1) body very slender and elongated; (2) urogomphi rather elongated, distinctly reaching outline of the body, directed outside; (3) rostrum elongated and slender; (4) setae more or less elongated; (5) head with one vs, two sos, two os; (6) rostrum with one or two sls and without or with one rs; (7) pronotum with two as, one ds, two sls, two ls, three or four pls; (8) meso- and metanotum with two or three setae; (9) abdominal segments I-VII dorsally with six or seven elongated, growing setae.

Remarks and comparative notes.

The adult of this species is characterised by elytra distinctly elongate, dorsal integument black or blue, sometimes with metallic reflections.

The shape of the body together with the colour of the dorsal integument are characters that this group shares only with M. heydenii . These two groups include the species of Mecinus not living on Plantago . Nevertheless, they seem to be not closely related on the basis of both a phylogenetic study of the adults and of molecular data as well as the examination of the immatures. The adults of the species related to M. janthinus are distinguishable from those related to M. heydenii by the less curved rostrum in lateral view, the shape of the penis, the distinctly longer flagellum and the completely unusual shape of the spermatheca that is reminiscent of the Cionini . The larvae and pupae differ in a series of characters in the chaetotaxy. Moreover, the immatures of this group possess some autapomorphies, i.e., in larvae four pds and usually three ss on the abdominal segments I-VIII and the surface of postlabium densely covered with asperities, and in pupae, the more or less elongated setae on the body and the abdominal segments I-VII dorsally with six or seven elongated, growing setae.