Velcro-Like System Used to Fix a Protective Faecal Shield on Weevil Larvae

Abstract

The last instar larva and pupa of Eucoeliodes mirabilis (A. Villa & G. B. Villa, 1835) (Curculionidae: Ceutorhynchini) are described using drawings and SEM images and are compared and keyed with already described larvae of 58 other ceutorhynchinae taxa. The larval body has an effective combination of morphological adaptations that assist a unique biological defensive strategy. All larval stages of E. mirabilis feed ectophytically on leaves of Euonymus europaeus L. (Celastraceae), and the larval body is covered with a thick faecal shield. The fixation of this protective shield on the larval back is performed by a peculiar dorsal microsculpture composed of a dense carpet of microtrichia on the thorax and abdomen, which serves effectively as a velcro system. Because of this strategy, macrosetae on the larval and pupal body of E. mirabilis are completely reduced. Larvae of E. mirabilis also have distinct morphological adaptations for protecting the spiracles against intrusion of faeces and avoiding occlusion of the tracheal system: a) microtrichia around spiracles are slightly shorter, distinctly stronger and are arranged with high-density and in clusters and b) spiracles are protected by an external safety valve. This strategy of E. mirabilis larvae is unique, although somewhat similar to that of Criocerinae and Blepharida-group leave beetles (Galerucinae) (both Coleoptera: Chrysomelidae), but with distinctly different morphological adaptations.

Description of the immature stages of two Mononychus species (Coleoptera: Curculionidae: Ceutorhynchinae) and a study of the host preferences of M. punctumalbum for Iris species in central Europe

“…The precise general description of larvae of the subfamily Ceutorhynchinae, which is summarized by nine character sets, was first published by May (): (i) head with des 3 on epicranial half; (ii) antennae hemispherical, fully exposed; (iii) endocarinal line absent; (iv) frons with only fs 4 developed; (v) labral rods separate, subparallel; (vi) postlabium with proximal pairs of plbs as far apart as median pair; (vii) abdominal spiracles with air‐tubes caudad; (viii) abdominal VIII spiracle lateral; and finally (ix) abdominal segments with ventral lobes developed as ambulatory ampullae. All these characters, with one exception, are consistent with known descriptions (Anderson, , ; Gosik, , , ; Lee & Morimoto, ; May, ; Miller, ; Nikulina, ; Orlova‐Bieńkowskaya, ; Prena et al., ; Scherf, ; Skuhrovec et al., ; Vayssieres, ). The only exception is that in the case of character number 4, rather than one well‐developed fs 4 seta on the frons, the larvae of Mononychus species have a short fs 4 on the frons as well as two additional minute setae ( fs 1 , and fs 2 ) (Figures a and a).…”

“…The larvae of 59 Ceutorhynchinae taxa in 23 genera have previously been described (Miller, ; Scherf, ; Anderson, , ; Vayssieres, ; May, ; Lee & Morimoto, ; Orlova‐Bieńkowskaya, ; Gosik, , , ; Nikulina, ; Prena et al., ; Skuhrovec, Stejskal, Trnka, & di Giulio, ). A detailed description of the pupa is known only for seven Ceutorhynchinae taxa (Anderson, ; Gosik, , ; Scherf, ; Skuhrovec et al., ).…”

“…The larvae of 59 Ceutorhynchinae taxa in 23 genera have previously been described (Miller, ; Scherf, ; Anderson, , ; Vayssieres, ; May, ; Lee & Morimoto, ; Orlova‐Bieńkowskaya, ; Gosik, , , ; Nikulina, ; Prena et al., ; Skuhrovec, Stejskal, Trnka, & di Giulio, ). A detailed description of the pupa is known only for seven Ceutorhynchinae taxa (Anderson, ; Gosik, , ; Scherf, ; Skuhrovec et al., ). The immature stages were compared with most of the species described or drawn by Anderson (, ), Scherf (), May (), Lee and Morimoto (), Orlova‐Bieńkowskaya (), Gosik (, , ), Nikulina () and Skuhrovec et al.…”

“…(); these illustrations are all of high or sufficient quality and therefore were very useful; however, the characteristics described are useful only for differential diagnosis. There were some differences in the descriptions of the larvae and pupae due to the use of different terminology for morphology and chaetotaxy and/or the absence of good‐quality drawings and data concerning some important morphological features (Skuhrovec et al., ).…”

“…Brisout de Barneville, 1869) and M. dimidiatus (Frivaldszky, 1865) with four fs ), Nikulina () ( C. subtilirostris Schultze, 1902 and C. viator Faust, 1885; larvae also have short but distinct fs 1 ) and Skuhrovec et al. () ( Eucoeliodes mirabilis (A. Villa & G. B. Villa, 1835) has four fs ).…”