Psyllids (Hemiptera: Psylloidea) in the entomological collection of the National Museum of Natural History, Bulgarian Academy of Sciences

: The entomological collection of the National Museum of Natural History at the Bulgarian Academy of Sciences in Sofia (NMNHS) preserves a total of 89 specimens representing 25 species of jumping plant lice (Hemiptera: Psylloidea). These were recorded and digitised in the Specify platform as part of the Distributed System of Scientific Collections project (DissCo-BG). This paper summarises all available data on these specimens. Twenty-four species were collected in Bulgaria, one species in Greece. Voucher specimens for Psylloidea published in a historical treatise on the Bulgarian fauna of Hemiptera by Dimitar Joakimov were not found in the NMNHS and are most likely lost. However, Joakimov’s collection, later acquired and supplemented by the museum, contains unpublished material, including three species reported here for the first time from Bulgaria: Aphalara maculipennis Löw, 1886, Cacopsylla ulmi (Foerster, 1848) and Dyspersa abdominalis (Flor, 1861).


Introduction
Jumping plant lice or psyllids (Hemiptera: Psylloidea) are small phytophagous insects that feed on the phloem of mainly dicotyledonous plants.There are over 4000 described species of psyllids worldwide, with the greatest diversity found in the tropics (Burckhardt et al., 2021).The Palaearctic psyllid fauna is considered well studied, with about 400 known species in Europe (Burckhardt, 2013;Serbina et al., 2015), of which less than a hundred have been reported from Bulgaria so far (Pramatarova et al., 2021).
The entomological collection of the National Museum of Natural History of the Bulgarian Academy of Sciences in Sofia (NMNHS) is one of the richest in the Balkan Peninsula (Popov, 1991) and includes about 20000 Hemiptera specimens (N. Simov, pers. comm.).The core of the historical Hemiptera collection was formed by material collected by Dimitar Joakimov (1864-1952), Nikola Nedjalkov (1852-1919) and Pencho Drenski (1886-1963) (Popov, 1999).Joakimov (1909) was also the first to publish faunistic data on psyllids from Bulgaria; he listed 17 species of Psylloidea from the country.However, due to numerous later changes in psyllid taxonomy, some of the species listed by Joakimov (1909) are doubtful and require a revision.
The aim of this paper is to identify the Psylloidea material available in the NMNHS and to summarise all relevant data.

Material and methods
All the material studied is in the entomological collection of the National Museum of Natural History, Bulgarian Academy of Sciences, Sofia (NMNHS).Several specimens were originally mounted on cardboard plates, while most of the others were pinned on entomological pins or minutiae on pieces of elderberry (Sambucus sp.) pith.The minutiae were often badly corroded and brittle.Therefore, as part of this study, some specimens of the psyllids were remounted and glued on cardboard plates.Some series of specimens were originally mounted on a single piece of elderberry pith and bore a handwritten label or just a number (cited by us in square brackets in the list of material below), probably corresponding to Joakimov's field notes, which are now no longer available.These specimens have been separated for identification and digitisation on a piece of white polyethylene foam, with new labels referring to the original.All specimens were digitised on a Specify collection management platform (https://www.specifysoftware.org/�) as part of the Distributed System of Scientific Collections project (DissCo-BG).Each specimen was labelled with softwaregenerated labels containing toponyms and collectors in Cyrillic script transliterated according to NMNHS collection rules.Separate labels were provided with human and machine readable, newly generated individual identification numbers according to NMNHS collection rules (e.g.BG-NMNHS-ENT-00000000001377 and QR code with the same content).In addition, a third label was applied with the current taxonomic identification of the specimen.All original labels of the specimens were kept on the pins.The transliterated locality and collector data of the specimens are used in the Results section.
The monographs by Ossiannilsson (1992) and Vondráček (1957) were mainly used for the identification of psyllids.Burckhardt et al. (2021), Cho et al. (2022) and Ouvrard (2023) were used for the classification and nomenclature of the psyllids.
Comments: Joakimov (1909) reported Aphalara exilis (Weber & Mohr, 1804) from Bulgaria (Sofia).However, his record might actually refer to A. nigrimaculosa, as both species are very similar, and the report was published before the taxonomic revision of the group by Burckhardt & Lauterer (1997).The latter authors also reported A. nigrimaculosa, but not A. exilis from Bulgaria.Apart from Bulgaria, A. nigrimaculosa is known from the Caucasus and Greece (Burckhardt & Lauterer, 1997).
Comments: Aphalara Foerster is considered a taxonomically difficult genus due to the minor morphological differences between species (Ossiannilsson, 1992;Burckhardt & Lauterer, 1997).Without additional male specimens or data on the host plant, the present material cannot be reliably identified.
Comments: Probably native to western Asia, introduced with its host plant, Ficus carica into many countries of the Mediterranean (including also Greece), western, central and southeastern Europe, Comments: Due to its poor condition, the specimen cannot be identified.