Mecinus collaris 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 collaris group

Differential diagnosis.

Larva. (1) slightly pressed dorso-ventrally, cuticle densely tuberculate, premental sclerite, pedal lobes and spiracular area of meso- and metathorax dark pigmented; (2) pedal lobes prominent well isolated; (3) abdominal segment X reduced to three anal lobes of equal size; (4) thoracic spiracle bicameral; (5) abdominal setae short; (6) abdominal segments I-VII with four pds and two ss (abd. segment VIII with one ss); (7) head brown, flattened laterally; (8) frontal suture visible; (9) endocarina 1/2 of the frons; (10) des4 minute or short; (11) presence of fs1; (12) absence of fs2; (13) fs3 minute; (14) head with one stemma; (15) presence of cls1; (16) labial palpi two-segmented; (17) premental sclerite cup-like; (18) surface of postlabium smooth.

Pupa. (1) body elongated; (2) urogomphi slender, rather short, reaching outline of the body, directed downward; (3) rostrum moderately elongated; (4) setae different in length; (5) head with one sos; (6) rostrum with one rs; (7) pronotum with two as, one ds, one sls, one ls, four pls; (8) meso- and metanotum with two setae; (9) abdominal segments I-IV without setae dorsally; segments V-VII dorsally with five growing setae.

Remarks and comparative notes.

The adults of this monobasic group are easily distinguishable from all other species of Mecinus by several autapomorphies, such as rostrum short and wide, straight in lateral view, scrobe not reaching anterior margin of eye, elytra elongate, broad scales densely covering base of pronotum, epimera and episterna. In contrast, immatures have few autapomorphies, i.e., larvae are slightly pressed dorsoventrally, with a densely tuberculate cuticle, whereas premental sclerite, pedal lobes and spiracular area of meso- and metathorax are dark pigmented; the pupae have abdominal segments I-IV lacking setae dorsally, whereas segments V-VII dorsally possess five growing setae.

Presently, it is unclear to which species M. collaris is more closely related. The other species with short and straight rostrum, such as those of the M. simus group, do not apparently share other synapomorphies with M. collaris . In contrast, the larvae of the latter share the number of palpomeres of the labial palpi (two) and the shape of the thoracic spiracle (bicameral) and abdominal spiracles (unicameral) with the M. janthinus group. The pupae of M. collaris differ from all the others studied here by the dorsal setae of the abdominal segments because segments I-IV are without setae and segments V-VII have setae growing gradually.