The genus Gymnetron from China with description of pre-imaginal stages of G. miyoshii, G. auliense and G. vittipenne (Coleoptera,Curculionidae)

Abstract

There are four species of Gymnetron in China recorded to date including Gymnetron miyoshii Miyoshi, 1922, Gymnetron villosipenne Roelofs, 1875, Gymnetron auliense Reitter, 1907 and Gymnetron vittipenne Marseul, 1876, of which the last two are new country records. The pre-imaginal stages including eggs, mature larvae and pupae of Gymnetron miyoshii, Gymnetron auliense and Gymnetron vittipenne are described and illustrated. In addition, their diagnostic characters (larvae and pupae) are discussed and differentiated, and notes on some of their biological parameters are provided. Potential ecological impacts between Gymnetron weevils and their host Veronica spp. also are provided.

The morphology of the preimaginal stages of Cleopomiarus micros (Germar, 1821) (Curculionidae, Coleoptera) and notes on its biology

“…The morphology of the L 3 larvae and pupa of C.micros does not differ from the typical characters of preimaginal stages of weevils of the tribe Mecinini (Emden 1938, Scherf 1964, Anderson 1973, Marvaldi 2003, 2005, Marvaldi and Lanteri 2005, Gosik 2010, Jiang and Zhang 2015). The morphology of mature C.micros larva is similar to the description of the characters of the third-stage larvae of the tribe presented by Emden (1938), including pronounced convexity of the body, a long, unbranched endocarina, which together with the epicranial suture extends two-thirds the length of the head, and an intersegmental thoracic spiracle.…”

“…As mentioned in the Introduction, the head of species of this tribe usually has 3 pairs of des. In C.micros there are 4 pairs, as in Rhinusabipustulata (Rossi, 1792) or Gymnetronmiyoshii Miyoshi, 1922 (Gosik 2010, Jiang and Zhang 2015). In Mecinini, the labial palpus usually has a single segment; if there are two segments the basal segment is not distinctly separated.…”

“…In the larvae, these are as follows: head usually with 3 distinct pairs of setae ( des ) and with long, unbranched endocarina, which together with the epicranial suture extends 2/3 the length of the head; labial palpus usually with 1 segment – if there are 2 segments the basal segment is not distinctly separated; hypopharynx with usually 4, less often 2 or 6 epithelial anteromedial setae; premental rounded, less often pointed; sclerites of the prosternum joined or free, numbering 0, 2, 4 or 6; thoracic and abdominal spiracles uni- or bicameral depending on the genus, abdominal spiracles located laterally on the intersegmental membrane, tubes well defined from atrium (Emden 1938, Scherf 1964, Anderson 1973, May 1993, Marvaldi 2003, 2005, Gosik et al 2010, Jiang and Zhang 2015). Species belonging to the Mecinini tribe are poly-, oligo- or monophages of plants of the families Campanulaceae, Scrophulariaceae and Plantaginaceae (Scherf 1964, Smreczyński 1976, May 1993, Burakowski et al 1997, Caldara 2001, Caldara et al 2014).…”

Immature stages of Palearctic Mecinus species (Coleoptera, Curculionidae, Curculioninae): morphological characters diagnostic at genus and species levels

“…Unfortunately, some descriptions previously published on immature stages of species belonging to other genera of Mecinini are somewhat problematic because of missing details about the chaetotaxy and/or the absence of quality drawings (see Skuhrovec et al 2018), making such comparisons still difficult. Only the recent descriptions of six Cleopomiarus and three Miarus species (Skuhrovec et al 2018;Szwaj et al 2018), three Gymnetron species (Jiang and Zhang 2015), and two Rhinusa species (Gosik 2010; Ścibior and Łętowski 2018) were sufficiently complete for such a comparison. Skuhrovec et al (2018) emphasised that the taxonomical interpretation of some characters (e.g., thoracic and abdominal dorsal setae) in the papers above is very disputable.…”

“…To date, larvae of only approximately 30 Mecinini species have been described, while descriptions of pupae have been made for 15 Mecinini species (see Skuhrovec et al 2018 for complete references). However, there are only a few detailed descriptions of larvae and pupae that can be used for an adequate taxonomic comparison; these include immatures of three species of Gymnetron (Jiang and Zhang 2015), two species of Rhinusa (Gosik 2010;Ścibior and Łętowski 2018), five species of Cleopomiarus (Skuhrovec et al 2018;Szwaj et al 2018) and three species of Miarus (Skuhrovec et al 2018). In fact, the comparison of approximately ten previously described immatures of mecinines, including two Mecinus species, M. heydenii Wencker, 1866 (Emden 1938) and M. janthinus Germar, 1821 (Scherf 1964), is somewhat problematic due to the absence of important details of the chaetotaxy and/or the absence of quality drawings.…”