Volume 119, Number 4, September and October 2008 325 ODOUR AND COLOUR SIMILARITY IN TWO SPECIES OF GREGARIOUS CARABID BEETLES (COLEOPTERA) FROM THE CRATI VALLEY, SOUTHERN ITALY: A CASE OF MÜLLERIAN MIMICRY? 1 Teresa Bonacci, 2 Pietro Brandmayr, 2 Renato Dalpozzo, 3 Antonio De Nino, 3 Alessandro Massolo, 4 Antonio Tagarelli, 3 and Tullia Zetto Brandmayr 2 ABSTRACT: Bombardier beetles of the genus Brachinus (Carabidae) are disagreeable prey because they discharge irritating quinones. Brachinus beetles live in aggregations and display warning colours. Like Brachinus beetles, Anchomenus dorsalis beetles produce methylsalicylate, and present a similar colour pattern. Anchomenus dorsalis beetles are usually found within Brachinus aggregations. Our aim was to investigate the similarity of cuticular chemical profiles of these two species to test the hypothe- sis of interspecific chemical mimicry. We investigated the cuticular composition of A. dorsalis, B. sclo- peta, and Poecilus cupreus. Poecilus cupreus, a non-aposematic carabid commonly found in Brachinus spp and Anchonemus dorsalis aggregations, was used as a control. The cuticular profiles of the three species include 48 different hydrocarbons. The cuticular hydrocarbon profiles of the three species of carabids were different, but individuals of Brachinus were chemically more similar to those of Ancho- menus than to those of Poecilus; in turn, individuals of Poecilus were more similar to Anchomenus than to Brachinus. We suggest that A. dorsalis is possibly mimicking the cuticular profile of B. sclopeta as an effective antipredator strategy. Brachinus sclopeta may benefit from a reduction of individual preda- tion risk due to an increased number of aggregated preys (dilution effect), while A. dorsalis may increase the benefit both from the dilution effect and from the greater chemical defense of B. sclopeta. KEY WORDS: gregariousness, aposematism, cuticular profile, Müllerian mimicry, Brachinus, Ancho- menus, Poecilus, Coleoptera, Carabidae, Crati Valley, Italy Müllerian mimicry, when at least two species share a warning pattern (Skelhorn and Rowe 2005), frequently involves different defense chemicals. In this form of mi- micry, the mimics that possess different defense chemicals are better protected than those that share a single defense chemical (Skelhorn and Rowe 2005) because they enhance predator learning and memory. In Müllerian mimicry, the species involved are sympatric and share the same or similar warning colour pattern (Wickler, 1968). Many animals use warning colours (or aposematism) to signal their dangerousness to potential predators (Cott, 1940; Guilford, 1990). Aposematic coloration decreas- es the probability of attack by naïve predators, as an effect of the novelty, a reac- tion to aversive colours (Coppinger, 1969, 1970; Roper and Cook, 1989; Gamber- ale and Tullberg, 1996 a, b), or both (Sillén-Tullberg, 1985). Experienced predators tend to avoid repeated contact with aposematic prey items (Gittleman and Harvey 1980; Roper 1994). ______________________________ 1 Received on October 29, 2007. Accepted on February 24, 2008. 2 Dipartimento di Ecologia, Università della Calabria 87036 Arcavacata di Rende (Cosenza) Italy. E-mails: (TB) t.bonacci@unical.it, (PB) brandmay@unical.it, and (TZB) tuzetto@unical.it, respec- tively. 3 Dipartimento di Chimica, Università della Calabria 87036 Arcavacata di Rende (Cosenza) Italy. E-mails: (RD) dalpozzo@unical.it, (ADN) denino@unical.it, and (AT) a.tagarelli@unical.it, respec- tively. 4 Dipartimento di Biologia Animale e Genetica, Università di Firenge, via Roma 17, I-50125, Firenze, Italy. E-mail: massolo@unifi.it. ENTOMOLOGICAL NEWS 119 (4): 325 September and October 2008 Mailed on November 12, 2008