The Tergal Gland Secretion of the Two Rare Myrmecophilous Species Zyras collaris and Z. haworthi (Coleoptera: Staphylinidae) and the Effect on Lasius fuliginosus
The beetle species Zyras collaris and Z. haworthi belong to the rove beetle tribe Myrmedoniini (Staphylinidae: Aleocharinae), which comprises many myrmecophilous species. Due to their rareness, it is unknown how the two species interact with their host ants. GC-MS analyses revealed that both species release α-pinene, β-pinene, myrcene and limonene from their defensive tergal glands. This composition of tergal gland secretion is unique within the subfamily Aleocharinae. In biotests, Lasius fuliginosus ants showed increased antennation towards filter paper balls treated with mixtures of these substances in natural concentrations. Because these monoterpenes are also present in some aphid species which are attended by ants, we hypothesize that Zyras beetles mimic the presence of aphids and thereby achieve acceptance by their host ants. 1. Introduction The rove beetles tribe Myrmedoniini (Staphylinidae: Aleocharinae) contains many myrmecophilous species. In Central Europe, it comprises the myrmecophilous genera Lomechusa and Lomechusoides, Zyras, Myrmoecia, and Pella, as well as the nonmyrmecophilous species Drusilla canaliculata Fabricius, 1787. Myrmoecia and Pella were formerly considered subgenera of Zyras but, meanwhile, have been elevated to genus rank [1–3], which is also supported by molecular data [4, 5]. Lomechusa and Lomechusoides are textbook examples for the integration of myrmecophiles in ant nests by the use of appeasement glands on their abdomen [6]. Different strategies are used by Pella species to escape from aggressions by their host ant Lasius fuliginosus (Latreille, 1798). While the Japanese species P. comes (Sharp, 1874) mimics the cuticular hydrocarbon (CHC) pattern of its host ant to be accepted [7], P. laticollis (M？rkel, 1845) employs a specific appeasing behaviour [8]. Pella cognata (M？rkel, 1842), P. funesta (Gravenhorst, 1806), and P. humeralis (Gravenhorst, 1802) repel ants by the use of their abdominal tergal gland. This tergal gland is only found within the Aleocharinae and is used by most species of the subfamily as defensive gland against aggressors [9]. In P. funesta and P. humeralis, the gland secretion specifically contains sulcatone, a panic alarm inducing pheromone of L. fuliginosus. By the release of this compound, beetles create an “ant free space” [8, 10]. In contrast to these species, only little is known on the biology of Zyras species, and it is unclear how they achieve acceptance by ants. For Z. collaris (Paykull, 1789) and Z. haworthi (Stephens, 1835), this is mainly due to their rarity. For South-West Germany,
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