Eur. J. Entomol. 110 (2): 339-353, 2013 | DOI: 10.14411/eje.2013.047

Specialized feeding of Euconnus pubicollis (Coleoptera: Staphylinidae: Scydmaeninae) on oribatid mites: Prey preferences and hunting behaviour

Paweł JAŁOSZYŃSKI1, Ziemowit OLSZANOWSKI2
1 Museum of Natural History, Wrocław University, Sienkiewicza 21, 50-335 Wrocław, Poland; e-mail: scydmaenus@yahoo.com
2 Department of Animal Taxonomy and Ecology, A. Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland; e-mail: olszanow@amu.edu.pl

Prey preferences and feeding-related behaviour of a Central European species of Scydmaeninae, Euconnus pubicollis, were studied under laboratory conditions. Results of prey choice experiments involving 50 species of mites belonging to 24 families of Oribatida and one family of Uropodina demonstrated that beetles feed mostly on ptyctimous Phthiracaridae (over 90% of prey) and only occasionally on Achipteriidae, Chamobatidae, Steganacaridae, Oribatellidae, Ceratozetidae, Euphthiracaridae and Galumnidae. The average number of mites consumed per beetle per day was 0.27 ± 0.07, and the entire feeding process took 2.15-33.7 h and showed a clear linear relationship with prey body length. Observations revealed a previously unknown mechanism for capturing prey in Scydmaeninae in which a droplet of liquid that exudes from the mouth onto the dorsal surface of the predator's mouthparts adheres to the mite's cuticle. Morphological adaptations associated with this strategy include the flattened distal parts of the maxillae, whereas the mandibles play a minor role in capturing prey. Mechanisms for overcoming the prey's defences depended on the body form of the mite. When attacking oribatids that adopt the ptychoid defence (encapsulation) Euconnus opened the prodorsum and pressed the anal and genital plates deeply into the idiosoma, whereas it fed on all other mites by entering their bodies through small gnathosomal or/and genital openings, after breaking off mouthparts or/and genital plates. The preferential feeding of a specialized and locally abundant ant-like stone beetle on one family of Oribatida, documented here for the first time, has implications for the population dynamics of the prey and raises questions about predator-prey co-evolution and costs of an unusually prolonged period spent feeding when at risk from competition and attack by larger predators, typical of the habitats where Scydmaeninae occur.

Keywords: Coleoptera, Staphylinidae, Scydmaeninae, Cyrtoscydmini, Euconnus, Palaearctic, prey preferences, feeding behaviour, Acari, Oribatida

Received: October 1, 2012; Accepted: January 2, 2013; Published: April 11, 2013

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