The present catalogue of the ants (Hymenoptera, Formicidae) of Bulgaria is made on a base of critical reconsideration of literature (covering the period from 1892 till 2009 and part of 2010) as well as on examination of the authors‘ and several museum‘s collections. A lot of data were omitted in the previous Bulgarian monograph on ants, lots of new data were recently added and many important additions and alterations were made due to taxonomic revisions of Eurasian Formicidae during the last three decades. Two new species are reported for the country [Temnothorax graecus (Forel, 1911) and Temnothorax cf. korbi (Emery, 1924)].This catalogue contains a list of 163 ant species belonging to 40 genera of 6 subfamilies now known from Bulgaria. Synonyms and information on the previously reported names in relevant publications are given. Known localities of the species are grouped by geographic regions. Maps with concrete localities or regions for each species were prepared. The conservation status of 13 ant species is given as they are included in IUCN Red List of Threatened Species and Bulgarian Biodiversity Act. In comparison with adjacent Balkan regions the ant fauna of Bulgaria is quite rich and its core is composed of South European elements.

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.

Entomopathogenic Myrmicinosporidium durum Hölldobler, 1933, a fungus known to exploit several ant species, is reported for the first time in five countries: Bulgaria, the Czech Republic, Romania, Slovakia, and Turkey. The discovery of the fungus in Anatolia significantly widens its known distribution. In addition, this fungal parasite was found to utilize two hitherto unknown host species: Tetramorium sp. D (sensu Schlick-Steiner et al. 2006) and Tetramorium sp. E (sensu Schlick-Steiner et al. 2006). According to the new data, M. durum seems to be more common in Europe than previously thought, while its host range is considerably larger. In the present paper, data on its currently known distribution and host preference are discussed.

The Maltese Islands are situated in the Central Mediterranean basin having a total land area of c. 316 km2. A diverse ant fauna is present in this archipelago, which is increasingly threatened by habitat degradation and invasion of alien species. The myrmecofauna of the archipelago has received considerable attention by researchers since 1893, bringing the total number to 59 species (Gómez 2017, Salata and Borowiec 2018), 11 of which are non-native. Confirmation of some already reported species, e.g. Messor structor (Latreille, 1798), Tapinoma nigerrimum (Nylander, 1856), Tetramorium caespitum (Linnaeus, 1758), is required in the light of recent taxonomic changes. Based on a critical literature review, older unpublished data (1995–1997) by one of us (DM), and newly collected ant material (mainly between 2015 and 2019) we provide an updated list of 70 ant species from the Maltese Islands. The specimens were collected by different techniques (e.g. direct sampling, sifting, MSS-traps, Malaise traps). Two ant species were recorded for the first time in the Maltese Islands and for five species we provide the first verified records. Seven morphospecies with unspecified taxonomic status were also collected and require further studies.

Aphaenogasterillyricasp. nov., a member of the A.subterranea species group, is described from Dinaric Alps of Slovenia and Croatia, from Golešnica Mt. in north Macedonia, Osogovo-Belasica Massif of southwestern Bulgaria, and from Kerkini Mts. of Greek Macedonia. It is characterised by large body size, moderately sculptured head, elevated mesonotum, and long propodeal spines. Its habitat preferences are discussed. A key to the Aphaenogastergraeca complex is provided.