The present catalogue of the ants (Hymenoptera, Formicidae) of Bulgaria is made on a base of critical reconsideration of literature (covering the period from 18

Messor is a diverse genus of Myrmicinae with 168 extant species and subspecies. In the Mediterranean, some of its taxa historically were classified as members of the Messor instabilis group (sensu Santschi), of which 19 are known from the eastern Mediterranean. Here, the Messor semirufus complex of the Balkan Peninsula that assembles a distinct subsection of members of the instabilis group is defined and treated. In total, five species are recorded, including three that are new. Messor atanassovii Atanassov, 1982 is redescribed and confirmed for Bulgaria (Thracian Plain, Struma, and Mesta Valley, Pirin Mt., and Eastern Rhodopi) and Greece (Epirus, Ionian Islands, Central and Eastern Macedonia, and Thraki). Three species are described as new to science: Messor danaes Salata, Georgiadis & Borowiec, sp. nov. (Cyclades: Serifos), Messor kardamenae Salata & Borowiec, sp. nov. (Dodecanese: Kos, Nisyros, Rhodes, and Tilos), and Messor veneris Salata, Georgiadis & Borowiec, sp. nov. (Cyclades: Milos). The fifth member of the complex, Messor creticus Borowiec & Salata, 2019, maintains its status of Cretan endemic.

The mutualistic interspecific relationships of trophobiosis between trophobiont planthoppers (Hemiptera, Fulgoromorpha) providing food to the host called xenobiont, are reviewed. The degree of interspecific relationships between these symbionts varies from occasional or short time duration (a few hours to a few days) to longer ones, with trophobionts left free to escape (optobiotic type) by the xenobiont, or maintained enclosed in nests or ant shelters (cryptobiotic type). Of 267 collected cases, 126 are new illustrated observations. Occasional trophobiosis is documented in 13 families of planthoppers and appears to be quite general in Fulgoromorpha, although it is reported for the first time for Dictyopharidae, Eurybrachidae, and Nogodinidae. Xenobionts associated with planthoppers are reported from ants and other Hymenoptera, Lepidoptera, and Blattodea, but also from Mollusca and even small gekkonid vertebrates. Tettigometridae appear to be exclusively tended by ants, while Fulgoridae significantly more often by cockroaches (40%) than by ants (27%). Long-time trophobiosis occurs always with ants, cryptobiotic ones reported in Cixiidae, Delphacidae, Tettigometridae, Meenoplidae, Flatidae and Hypochthonellidae, while optobiotic ones remain restricted to tettigometrids. A particular focus on Tettigometridae attended by ants is provided with new etho-ecological observations of 92 currently described tettigometrids species, 32 different species (35%) are now known to be able to be ant-attended. In Bulgaria, where fourteen species occur, trophobiosis occurs with at least five species of them (36%). In tettigometrids, subsociality, sessility, and underground life appear to be key factors allowing more complex relationships with ants. However, the planthopper size and thus the amount of food (drops of honeydew) is probably also an important factor. This might explain many new observations in large-sized and often isolated fulgorids with cockroaches. Tapping of trophobiont forewings by cockroaches, moths, or of the bark subtrate by geckos has been observed, but antennal palpation behaviours by ants are the most commonly observed with tettigometrids, although not with larger planthoppers. In tettigometrids, specific tegumentary glands secretions (allomones) of the abdomen pleurites might also mediate their long-term mutualistic associations, even possibly completing honeydew kairomones actions mediating planthopper trophobiosis in general.

The rich myrmecofauna in Bulgaria, comprising about 170 species, constitutes favorable settings for a diverse associated fauna. An attempt to summarize the fragmented faunal data on this ecological group in Bulgaria, together with inclusion of new data, has resulted in a comprehensive list of 121 beetle species from 14 families, obligate or facultative ant related. The extent of current knowledge on the various beetle families, host specificity, the nature of relations between guests and their ant hosts, and the regional characteristics of the myrmecophilous fauna are discussed.

This study presents a new design of sensor tool to record substrate-borne vibrations produced by insects. We applied a piezo element acting as a contact microphone connected to a digital recorder to detect the signals emitted by insects. A suitable 3D printed microphone box with a mechanism of connection to the substrate or to soft tweezers holding the insect is created. We found that the recordings of the low-frequency signals (up to 20 кHz) were sufficiently good for analysis and, at the same time, a much faster and easier method than the common ones of detecting micro-vibrations using a piezoelectric sensor and, importantly, is incomparably cheaper than using a laser vibrometer. This setup is suitable for the detection and structural description of signals emitted by insects and other arthropods. Oscillograms, spectrograms and audio files of the recorded signals of selected ants (Manica rubida, Latreille, 1802, Messor wasmanni Krausse, 1910, Myrmica ravasinii Finzi, 1923) and Ponera coarctata (Latreille, 1802)), an ant nest beetle (Paussus turcicus I. Frivaldszky von Frivald, 1835), a planthopper (Orosanga japonica (Melichar, 1898)) and a jumping plant louse (Bactericera perrisii Puton, 1876) are provided to demonstrate the effectiveness of the created equipment. The recordings from stridulation in Myrmica ravasinii, Manica rubida, Ponera coarctata and Paussus turcicus and the male call song of Orosanga japonica represent the very first documented signal production for these species. A scheme of the contact microphone and its mode of connection is shown. The research presented will democratise biotremological methods for the needs of integrative taxonomy and behavioural ecology, providing a broader understanding of vibrational signals through an efficient, accessible and operational method for both professional and citizen scientists.

The intranidal myrmecophilous arthropod fauna of the Maltese Islands is reviewed. Thirty species from nine orders are found to be obligate myrmecophiles, of which four species are recorded from the Maltese archipelago for the first time: Phrurolithus sp. (Araneae: Phrurolithidae), Pogonolaelaps canestrinii (Berlese, 1904), Gymnolaelaps messor Joharchi, Halliday, Saboori & Kamali, 2011 and G. myrmecophilus (Berlese, 1892) (Mesostigmata: Laelapidae). Phrurolithus also represents the first record of the family Phrurolithidae in Malta. Notes on the biology and local distribution of each species are provided, including ant-myrmecophile associations, of which two appear to be previously unknown: the occurrence of Smynthurodes betae Westwood, 1849 (Hemiptera: Aphididae) in the nest of Plagiolepis pygmaea (Latreille, 1798) and Phrurolithus in the nest of Pheidole pallidula (Nylander, 1849). Fourteen additional species are found to be either only occasionally myrmecophilic, accidental ant-guests or potentially myrmecophilous, the latter remaining ambiguous due to a lack of knowledge of their biology. Of these, the family Caeculidae (Arachnida: Trombidiformes) represents a new record for the Maltese Islands, on the basis of Microcaeculus sp. occurring in a nest of Camponotus barbaricus Emery, 1905. Preliminary results indicate that Messor nests may be repositories of considerable myrmecophile diversity, with the most unique symbionts.