Selection of Terrestrial Gastropod Prey by Cychrine and Pterostichine Ground Beetles (Coleoptera: Carabidae)

Abstract

The Canadian Entomologist 125: 463472 (1993) I examined the relative feeding preferences of five carabid beetle species for terrestrial gastropod prey. Scaphinotus marginatus Fischer, thought to be a snail specialist, discriminated among seven species of potential prey by size and species, with the slug Deroceras reticulatum (Miiller) being the most preferred. Scaphinotus marginatus appears to use its elongated and narrowed mouthparts, head, and thorax to prey upon terrestrial snails without having to crush their shells. The relative feeding preferences of four pterostichine generalist predators (Pterostichus adstrictus Eschscholtz, P. pensylvanicus LeConte, P. protractus LeConte, and P. surgens LeConte) for two species of small snails [Discus cronkhitei (Newcomb) and Euconulus fulvus (Miiller)] also were examined. Although all four carabids ate E. fulvus in varying proportions, only P. protractus consumed D. cronkhitei. I suggest that snail shell thickness and differing feeding preferences affect which snail species are eaten by these pterostichines. Digweed, S.C. 1993. Predation selective de gastropodes terrestres par des carabes cychrines et ptCrostichinCs (Coleoptera: Carabidae). The Canadian Entomologisl 125: 463472. Resume J'ai CtudiC les prCfkrences alimentaires relatives pour certains gastropodes terrestres chez cinq especes de carabes. Scaphinotus marginatus Fischer, rCputC Ctre un consommateur spkcialiste de gastropodes, peut discriminer entre sept especes de proies potentielles en fonction de leur taille et de leur nature spCcifique, et manifeste une prCfCrence pour la limace Deroceras reticulatum (Miiller). Scaphinotus marginatus semble utiliser ses pieces buccales allongkes et Ctroites, sa tete et son thorax pour attraper des gastropodes terrestres sans avoir a en Ccraser la coquille. Les prCfCrences relatives de quatre carabes ptCrostichinCs genkralistes (Pterostichus adstrictus Eschscholtz, P. pensylvanicus LeConte, P. protractus LeConte et P. surgens LeConte) pour deux especes de petits gastropodes [Discus cronkhitei (Newcomb) et Euconulus fulvus (Miiller)] ont Cgalement Ct C examinCes. Bien que les quatre carabes consomment des E. fulvus dans des proportions diffkrentes, seul P. protractus consomme des D. cronkhitei. Je crois que i'kpaisseur de la coquille des gastropodes et des prkfkrences alimentaires variCes dkterminent quelles especes de gastropodes sont consommCes par ces carabes ptkrostichinCs. [Traduit par la rkdaction]

Influence of slug defence mechanisms on the prey preferences of the carabid predator Pterostichus melanarius (Coleoptera: Carabidae)

“…This corroborates the findings of Kielty et al (1999) and Digweed (1993), who studied feeding preferences of carabid beetles on aphids and collembolans, and terrestrial snails. The missing effect of sex might liberate further researchers from considering it in experimental design, and thus considerably reduce the requirements for material.…”

“…Other species of nonspecialised ground beetles have been examined in former studies as control agents or used as model predators of slugsi.e. Abax parallelepipedus (Symondson, 1989(Symondson, , 1994Asteraki, 1993;Symondson & Lidell, 1993a), Scaphinotus striatopunctatus (Altieri, 1982;Digweed, 1994), S. marginatus (Digweed, 1993), Pterostichus madidus (Asteraki, 1993;Ayre, 2001;Mair & Port, 2001, 2002, P. niger (Pakarinen, 1993b), P. adstrictus, P. pensylvanicus, P. protractus, P. surgens (Digweed, 1993), Nebria brevicollis (Ayre, 2001;Mair & Port, 2001, 2002, Harpalus rufipes, H. aeneus (Ayre, 2001). However, these species either do not occur in the Czech Republic or were not available in as high numbers as P. melanarius.…”

“…This should influence prey preference of the ground beetles. Former studies have investigated single defence mechanisms (Martin et al, 1983;Deyrup-Olsen et al, 1986;Pakarinen, 1992Pakarinen, , 1993aSymondson, 1997;Mair & Port, 2002) or dealt with separate factors influencing prey preferences of ground beetles (Pollet & Desender, 1985;Digweed, 1993;Ayre, 2001;McKemey et al, 2001;Langan et al, 2001). This study compares the preference of Pterostichus melanarius Illiger, 1798 among five slug species while controlling for the hunger level of the predator, temperature, day/light period, condition of slugs and beetles, weights of slugs and beetles, sex of the beetles and predator-prey encounter rates (Wareing & Bailey, 1985;Ernstig & Vanderwerf, 1988;Wheater, 1988aWheater, , 1991Wallin & Ekbom, 1994;Ayre, 2001;McKemey et al, 2001, McKemey et al, 2003.…”

Dynamics of a Structured Slug Population Model in the Absence of Seasonal Variation

“…However, experimental evidence does suggest that prey selection is a function of size, with very small slugs and very large slugs not preyed upon. 16 If we let x p be the slug mass most preferred by beetles then, consistent with the limited data, 16 an appropriate smooth and normalised, prey selection function with compact support is 6) and 0 otherwise. Here 2x w is the full width of the sinusoidal peak.…”

“…2.3 below) of slug sizes. Although slugs are prey to a large number of opportunistic species, in agricultural settings the principle predator is the carabid beetle Pterostichus melanarius; 11,16,38 like all main predators of slugs, carabid beetles will readily switch to alternative food sources in their absence. 26 Although there is some weakly significant evidence to suggest that between-year beetle population growth is positively related to slug abundance, 38 it occurs over a long time scale and likely is mitigated by beetle migration.…”