Mecinus simus 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 simus group

Differential diagnosis.

Larva. (1) cuticle of the body smooth; (2) pedal lobes prominent; (3) abdominal segment X reduced to three anal lobes of equal size; (4) thoracic spiracle unicameral; (5) all abdominal setae short or very short, without trend to become progressively longer from abd. segment I to VIII; (6) abdominal segments I-VIII with three pds and two ss; (7) head white, rounded; (8) frontal suture poorly developed; (9) endocarina 3/4 of the frons; (10) des4 three times shorter than des1; (11) absence of fs1; (12) absence of fs2; (13) fs3 three times shorter than fs4; (14) head with one stemma; (15) absence of cls1; (16) labial palpi one-segmented; (17) premental sclerite cup-like, posterior extension with elongated, acute apex; (18) surface of postlabium smooth.

Pupa. (1) body stout and short; (2) urogomphi extremely short, not reaching outline of the body; (3) rostrum short, tapering to the top; (4) setae minute, almost invisible; (5) head with one os; (6) rostrum with one rs; (7) pronotum with two as, one ds, one ls, three pls; (8) meso- and metanotum with two setae; (9) abdominal segments I-VII with three setae dorsally and without setae ventrally.

Remarks and comparative notes.

The very short, conical and in lateral view straight rostrum, and the protibiae with apical third distinctly enlarged, sometimes with outer margin and apex bearing stout denticles, are truly noteworthy and unique in Mecinini . Both characters are oddly similar to those of a mole, and the tibiae are similar to those of Scarabaeidae . Since nothing was known about their biology except for their host plants, Caldara and Fogato (2013) speculated on the possibility that the species of this group deposit eggs in plant roots. The new biological data on M. pirazzolii below reported exclude this hypothesis and suggest that most likely the female is able to approach as close as possible to the pistil of the flower and deposit the egg thanks to the shape of its protibiae, since it is regularly found deeply stuck between Plantago inflorescences. This group might be related to the M. collaris group on the basis of the morphological characters of the adults ( Caldara et al. 2013), whereas it seems more related to the M. circulatus group according to the preliminary molecular data (I. Toševski, unpublished data). Unfortunately, the study of immatures did not clarify this situation. In fact, the presence of one palpomere on the labial palpi and of all spiracles unicameral contradicts this hypothesis, and the same combination of these two characters is found only in M. pascuorum and M. heydenii groups, with the former of which the M. simus group might have major similarities. However, the immatures of the M. simus group have some autapomorphies, such as a smooth body cuticle and prominent pedal lobes in larvae and abdominal segments I-VII with three setae dorsally and without setae ventrally, apart from an obvious extraordinarily short rostrum tapering to the apex in pupae.