Mecinus heydenii 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 heydenii group

Differential diagnosis.

Larva. (1) cuticle of the body tuberculate; (2) pedal lobes weakly isolated; (3) abdominal segment X reduced to three anal lobes of those lateral are the largest, and dorsal the smallest (sometimes absent); (4) thoracic spiracle unicameral; (5) abdominal setae very short to medium, become progressively longer from abdominal segment I to VIII; (6) abdominal segments I-VIII with three pds and two ss; (7) head brown, flattened laterally; (8) frontal suture poorly or well visible; (9) endocarina 4/5 of the frons; (10) des4 three times shorter than des1; (11) fs1 usually absent; (12) absence of fs2 except one species; (13) fs3 very short; (14) head with two stemmata; (15) absence of cls1; (16) labial palpi one-segmented; (17) premental sclerite U-shaped; (18) surface of postlabium smooth.

Pupa. (1) body very slender and elongated; (2) urogomphi short, only slightly reaching outline of the body, directed downward; (3) rostrum slender and elongated; (4) setae minute; (5) head with one os; (6) rostrum with without or with one sls and one rs; (7) pronotum with without or with up to two as, one ds, without or with one sls, without or with one ls, three pls; (8) meso- and metanotum with three setae; (9) abdominal segments I-VII with three or five setae dorsally.

Remarks and comparative notes.

The adults of this group are characterised by the rostrum in the basal half strongly and abruptly curved, the elytra distinctly elongate, and the dorsal integument black or blue, usually with metallic reflections apart from several characters of the male and female genitalia. In immatures, the autapomorphies seem limited to a U-shaped premental sclerite in larvae.

This group seems more closely related to the M. janthinus group than to other groups of Mecinus in both morphological characters (shape of body and colour of dorsal integument) and biology (hosts in Plantaginaceae other than Plantago ). However, the species of the M. heydenii group clearly differ from those of the M. janthinus group by the rostrum being strongly curved in the basal half and by the shape of the penis and spermatheca. The study of immatures also did not show close relationships between these two unique groups living on Antirrhineae , since the species of the M. heydenii group have one palpomere on the labial palpi instead of two, and all spiracles are unicameral. The pupae also differ somewhat in the shape of the urogomphi, which are shorter, only slightly reaching the outline of the body, and directed downward. The setae of the head and pronotum are also shorter, and the dorsal setae of abdominal segments I-VII are less numerous.