Abstract
Platycranus metriorrhynchus Reuter, 1883, the first representative of the predominantly Holomediterranean plant bug genus, Platycranus Fieber, 1870 is reported as a new element of the Hungarian true bug fauna. Diagnostic characters and bionomics of the species are discussed.
Introduction
The cimicomorphan family Miridae Hahn, 1833 with its approximately 11,000 described species is one of the eleven hyper-diverse insect families of the World (Cassis and Schuh, 2012). Representatives of the family are distributed in all biomes with temperate and warm climate and play diverse roles in ecosystems (Henry and Wheeler, 2019). Several species among them are of agricultural importance either as pests of cultivated crops or beneficial control agents of harmful weed or arthropod populations (Wheeler, 2000, 2001). Furthermore, new data elucidated the role of some species in pollination of dicotyledonous plants (Etl et al., 2022; Garcia et al., 2023). However, the true scale of the importance of plant bugs is hard to assess due to the deficiencies in taxonomic and faunistic knowledge of the mirid true bugs in many regions which is a prerequisite of exploratory and applied ecological studies.
The Pannonian biogeographic region can be considered as one of the less known territories in terms of its plant bug diversity because in course of the nearly 150-years research history of the Heteroptera fauna of the Carpathian basin the study of this family was virtually neglected. Besides the authoritative enumerations of the heteropteran insects of the Hungarian Kingdom by Horváth (1897), and the most recent checklist of the Heteroptera of Hungary (Kondorosy, 1999, 2005), knowledge regarding the composition of mirid true bug fauna of the county was resulted by faunistic surveys of specific areas, study of insect assemblages colonizing particular plant cultures, and data resulting from conservation and community ecological studies with the occasional reports of new faunal elements as reviewed by Kóbor (2021). Currently 291 species of family Miridae are recorded from Hungary which accounts for approximately one-third of the total Heteroptera fauna. However, this number will certainly increase in the future by 1) recording previously unnoticed indigenous species; 2) human-mediated introduction of alien species; and 3) area expansion of Mediterranean species as a result of climate change (Bale et al., 2002; Rabitsch, 2008a, b; Régenière et al., 2012; Putshkov, 2013; Tabak et al., 2017).
The representatives of the genus Platycranus Fieber, 1870 are small to medium-sized true bugs belonging to the subfamily Orthotylinae Van Duzee, 1916. The genus is currently consisting of two subgenera – Platycranus Fieber, 1870 and Genistocapsus Wagner, 1955 – with 13 currently valid species after the profound revisionary work of Knyshov and Konstantinov (2013). Species included are associated with the legume tribe Genistae (Fabaceae; sensu Polhill, 1976) and are distributed mostly in the Euromediterranean region, except Platycranus bicolor (Douglas and Scott, 1868) known from Western Europe with the northernmost records from Ireland and Platycranus remanei Wagner, 1955 with its distribution reaching Ukraine in the East (Knyshov and Konstatinov, 2013).
The present study reports the first occurrence of the species Platycranus metriorrhynchus Reuter, 1883 as the first known representative of the genus and the northernmost record of the species from Hungary with notes on its bionomics, importance and possibility of the occurrence of further Platycranus species.
Material and methods
The specimen studied was collected in course of the monitoring of the Heteroptera fauna in the Soroksár Botanical Garden, Budapest, Hungary (GPS: 47°23′58.4″N 19°09′14.1″E; Figs 1–3). The specimen is deposited in the author's personal collection (PCPK – Personal Collection of Péter Kóbor, HUN–REN Centre for Agricultural Research, Plant Protection Institute, Budapest, Hungary).
Collection site of P. metriorrhynchus in Hungary: 1. Location of the Soroksár Botanical Gardens; 2. map of the study site; 3. photo of the sand steppe habitat fragment (map source: https://www.openstreetmap.hu/; habitat photo was taken by the author)
Citation: Acta Phytopathologica et Entomologica Hungarica 58, 2; 10.1556/038.2023.00198
Exoskeletal characters were studied, and photomicrographs were done with Kern Optics OZL 466 stereoscopic microscope. Photomicrographs were done with Keyence VHX 5000 digital microscope.
The specimen was identified, and the morphology was adapted from Wagner (1974) and Knyshov and Konstatinov (2013). Bibliographic, distribution and host plant data were compiled based on Kerzhner and Josifov (1999), Aukema et al. (2013), Knyshov and Konstantinov (2013), and the Plant Bug Planetary Biodiversity Inventory (Schuh, 2023). Terminology for chorotypes was adapted from Heiss and Josifov (1990).
Results
Family Miridae Hahn, 1833
Subfamily Orthotylinae Van Duzee, 1916
Tribe Orthotylini Van Duzee, 1916
Genus Platycranus Fieber, 1870
Type species: Platycranus erberi Fieber, 1870: 252 (by monotypy)
Diagnosis. Platycranus can be readily distinguished from other Hungarian representatives of Orthotylinae with the combination of the following characters: head conspicuously wide (almost as wide as pronotum in males) with relatively flat vertex and transversal keel at base; pubescence consisting of the combination of short, semierect and longer scale-like setae. Detailed generic diagnosis is provided in the revision of Knyshov and Konstantinov (2013).
Distribution. Predominantly Euro-Mediterranean with northernmost records from Ireland, westernmost records form the Canary Islands and Portugal, and easternmost records from Ukraine, Israel and Jordan.
Notes. The genus was subdivided into two subgenera, i.e., Platycranus and Genistocapsus by Wagner (1956) based on the combination of the following characters: labium in subgenus Platycranus short, at most slightly surpassing fore coxae (in Genistocapsus, labium at least reaching middle coxae); in Platycranus head elongate with vertex flat (in Genistocapsus head short, declivent with vertex and clypeus somewhat concave); eyes in Platycranus large compared to the width of head (ratio: 1: 0.9–1.9) and protruding above vertex in males (eyes in males of Genistocapsus smaller compared to the width of head (ratio: 1: 1.5–2.7), not protruding above vertex).
Subgenus Genistocapsus Wagner, 1956: 421, 424
Type species: P. metriorrhynchus Reuter, 1883 (by original designation)
P. metriorrhynchus Reuter, 1883: 252
Dorsal habitus (4) and lateral view (5) of P. metriorrhynchus (female, PCPK)
Citation: Acta Phytopathologica et Entomologica Hungarica 58, 2; 10.1556/038.2023.00198
Detail pictures of P. metriorrhynchus (female, PCPK): 6. pattern of head in frontal view; 7. cuneus and membrane of hemelytron (images are not to scale)
Citation: Acta Phytopathologica et Entomologica Hungarica 58, 2; 10.1556/038.2023.00198
Studied material: “Soroksár Botanical Gardens, Budapest, sweep netting in sand steppe, 30. vi. 2023” (1f, PCPK).
Diagnosis. Head mostly pale green with irregular spots at base of vertex adjacent to compound eyes, a large blackish region on the anterior part of vertex and clypeus interrupted by a pale green drop-shaped spot medially (Fig. 6). Antennomere I black, antennomere II brown with apex blackish, antennomere III-IV dark brown. Labiomeres fuscous. Thorax predominantly greenish brown. Pronotum with anterior margin pale green and pronotal callosities black. Cuneus with irregular dark brown spot continuing in a fading band along the apical margin of corium (Fig. 7). Femora black with apex brown, tibiae fuscous, tarsomeres black. Abdomen mostly pale green with irregular ochraceous markings on segments. Habitus moderately elongate, integument covered with yellow scale-like pubescence; total body length: 3.93 mm. Head triangular in dorsal view, vertex and clypeus roundly declivent in lateral view. Ratio of antennomere I to width of vertex: 1: 0.45; ratio of antennomere II to width of vertex: 1: 1.59. Labiomeres reaching the middle coxae. Pronotum trapeziform, anterior margin obscuring the collar dorsally. Pronotal callosities well-defined, slightly bulging. Pronotum width to length ratio: 1: 1.91; ratio of width of pronotum to width of head: 1: 1.15. Macropterous, hemelytra reaching apex of abdomen. Membrane with a large and small, almost indistinct closed cell; integument finely wrinkled. Tarsal claws evenly curved with pulvilli reaching almost the midline; parempodia strap-like, converging apically.
Similar species. Another species subgenus Genistocapsus having records from the region and possibly occurring in Hungary is P. remanei Wagner, 1955, known from Slovenia (Knyshov and Konstantinov, 2013) which can be readily distinguished from P. metriorrhynchus based on the lack of extended brown pattern of dorsum (dorsum of P. remanei is uniformly greenish yellow.).
Distribution. South European with known area ranging from Portugal (West) to Bulgaria (East) with northernmost records from Trentino-Alto Adige and Friuli-Venezia Giulia regions of Italy; generally considered as montane species (Kment, 2013; Knyshov and Konstatinov, 2013).
Host plant associations. P. metriorrhynchus is known from multiple legume species belonging to genera Cytisus, Genista, and Sarothamnus (for a detailed list see Knyshov & Konstantinov 2013).
Discussion
The present study reports the first occurrence of the plant bug species P. metriorrhynchus – as well as of the genus Platycranus itself – from Hungary. Though the study of genital character – which are considered as pivotal in species-level identification of mirid true bugs – was not (only one female was collected), other diagnostic characters (e.g., coloration pattern of antennae, proportions of body parts) were consistent with those discussed in available literature (e.g., Wagner, 1974; Knyshov and Konstatinov, 2013). Considering the circumstance of collecting, i.e., the distance between the study site and the northernmost previously published records in Italy, Central Dalmatia and Serbia (Protíc, 2011; Kment, 2013; Knyshov and Konstantinov, 2013) the presence of host plants in the Hungarian flora, e.g., Genista tinctoria and Cytisus scoparius; and the South European chorotype of the species with northernmost occurrences south of the line of the Alps mountain range the appearance of the species can be explained either by older but unnoticed presence or more recent northwards expansion. The former can be attributed to deficient knowledge regarding the mirid true bug fauna of Hungary, while the latter can be explained by the northward expansion of Mediterranean species, i.e., the phenomenon of “mediterranization” in Central European insect faunas (Rabitsch, 2008b; Putchkov, 2013). On the other hand, the possibility of translocation with ornamental plants also cannot be excluded though it is rather unlikely because none of the host plants of the species – viz. Cytisus and Genista species – were not planted in the past years (Mária Höhn, pers. comm.).
Acknowledgements
The author would like to thank the help of Mária Höhn (Hungarian University of Agricultural and Life Sciences, Buda Campus) professional manager of the Soroksár Botanical Gardens for providing the research permission. Furthermore, the author would like to thank the comments and suggestions of Artur Taszakowski (University of Silesia in Katowice) and Wolfgang Rabitsch (Universität Wien) which greatly helped to develop the initial manuscript.
The author's work was supported by the ÚNKP-23-4 New National Excellence Program of the Ministry for Culture and Innovation from the source of the National Research, Development and Innovation Fund.
References
Aukema, B., Rieger, C., and Rabitsch, W. (2013). Catalogue of palaearctic Heteroptera. Supplement. Vol. 6. Netherlands Entomological Society, Amsterdam, i-xxiii, pp. 1–629.
Bale, J.S., Masters, G.J., Hodkinson, I.D., Awmack, C., Bezemer, T.M., Brown, V.K., and Good, J.E. (2002). Herbivory in global climate change research: direct effects of rising temperature on insect herbivores. Global Change Biology, 8(1): 1–16.
Cassis, G. and Schuh, R.T. (2012). Systematics, biodiversity, biogeography, and host associations of the Miridae (Insecta: Hemiptera: Heteroptera: Cimicomorpha). Annual Review of Entomology, 57: 377–404.
Douglas, J.W. and Scott, J. (1868). British Hemiptera: additions and corrections. Entomologist's Monthly Magazine, 4: 265–271.
Etl, F., Kaiser, C., Reiser, O., Schubert, M., Dötterl, S., and Schönenberger, J. (2022). Evidence for the recruitment of florivorous plant bugs as pollinators. Current Biology, 32(21): 4688–4698.
Fieber, F.X. (1870). Dodecas neuer Gattungen und neuer Arten europäischer Hemiptera. Verhandlungen der Kaiserlich-Königlichen Zoologisch-Botanischen Gesellschaft in Wien, 20: 243–264, pls. 5–6.
Garcia, L., Gould, J., and Eubanks, M. (2023). Bugs carry pollen too: pollination efficiency of plant bug Pseudatomoscelis seriatus (Hemiptera: Miridae) visiting cotton flowers. Florida Entomologist, 106(2): 122–128.
Hahn, C.W. (1833). Die wanzenartigen Insecten. C. H. Zeh, Nürnberg, 1: 119–236.
Heiss, E. and Josifov, M. (1990). Vergleichende Untersuchung über Artenspektrum, Zoogeographie und Ökologie der Heteropteren-Fauna in Hochgebirgen Österreichs und Bulgariens. Berichte des Naturwissenschaftlichen–Medizinischen Verein Innsbruck, 77: 123–161.
Henry, T.J. and Wheeler, A.G. (2019). Family Miridae Hahn, 1833 (= Capsidae Burmeister, 1835): the plant bugs. In: Henry, T.J. (Ed.), Catalog of the Heteroptera or true bugs of Canada and the continental United States. CRC Press, pp. 251–507.
Horváth, G. (1897). Ordo Hemiptera. In: A Magyar Birodalom Állatvilága (Fauna Regni Hungriae). Királyi Magyar Természettudományi Társulat, Budapest, pp. 1–64.
Kerzhner, I.M. and Josifov, M. (1999). Cimicomorpha II. In: Aukema, B. and Rieger, C. (Eds.), Catalog of the Heteroptera of the Palearctic region. The Netherlands Entomological Society, Amsterdam, pp. 1–577.
Kment, P. (2013). Prvi nalaz biljne stjenice Platycranus metriorrhynchus (Hemiptera: Heteroptera: Miridae) u Hrvatskoj. Natura Croatica: Periodicum Musei Historiae Naturalis Croatici, 22(2): 333–337.
Kóbor, P. (2021). A review of the plant bug genus Macrotylus distributed in Hungary (Heteroptera: Miridae). Acta Phytopathologica et Entomologica Hungarica, 56(2): 187–200.
Kondorosy, E. (1999). Checklist of the Hungarian bug fauna (Heteroptera). Folia Entomologica Hungarica, 60: 125–152.
Kondorosy, E. (2005). New true bug species in the Hungarian fauna (Heteroptera). Folia Entomologica Hungarica, 66: 17–22.
Knyshov, A. and Konstantinov, F.V. (2013). A taxonomic revision of the genus Platycranus Fieber, 1870 (Hemiptera: Heteroptera: Miridae: Orthotylinae). Zootaxa, 3637(3): 201–253.
Polhill, R.M. (1976): Genisteae (Adans.) Benth. and related tribes (Leguminosae). Botanical Systematics, 1: 143–368.
Protić, L. (2011). New Heteroptera for the fauna of Serbia. Bulletin of the Natural History Museum, 4: 119–125.
Putchkov, P.V. (2013). Invasive true bugs (Heteroptera) established in Europe. Український ентомологічний журнал (Ukrainian Entomological Journal), (2): 11–28.
Rabitsch, W. (2008a). Alien true bugs of Europe (Insecta: Hemiptera: Heteroptera). Zootaxa, 1827: 1–44.
Rabitsch, W. (2008b). The times they are A-Changin': driving forces of recent additions to the Heteroptera fauna of Austria. In: Grozeva, S. and Simov, N. (Eds.), Advances in Heteroptera research. Pensoft Publishing, Sofia, pp. 309–326.
Régniére, J., St-Amant, R., and Duval, P. (2012). Predicting insect distributions under climate change from physiological responses: spruce budworm as an example. Biological Invasions, 14: 1571–1586.
Reuter, O.M. (1883). Trois nouvelles especes de Capsides de France. Revue d'Entomologie, Caen, 2: 251–254.
Schuh R.T. (2023). PBI plant bug: on-line systematic catalog of plant bugs (Insecta: Heteroptera: Miridae) (version Mar 2013). Available at: https://research.amnh.org/pbi/catalog/index.php(Accessed: 28 September 2023).
Tabak, M.A., Piaggio, A.J., Miller, R.S., Sweitzer, R.A., and Ernest, H.B. (2017). Anthropogenic factors predict movement of an invasive species. Ecosphere, 8(6): e01844.
Van Duzee, E.P. (1916). Synoptical keys to the genera of North American Miridae. University California Publications in Entomology, Technical Bulletin, 1: 199–216.
Wagner, E. (1955). Neue Platycranus-Arten aus Südfrankreich und Spanien (Het. Miridae). Revue Francaise d'Entomologique, 22: 127–133.
Wagner, E. (1956). 21. Familie: Miridae (Capsidae auct.), Fortsetzung. In: Gulde, J. (Ed.), Die Wanzen Mitteleuropas, 11: 321–480.
Wagner, E. (1974). Die Miridae Hahn, 1831, des Mittelmeerraumes und der Makaronesischen Inseln (Hemiptera, Heteroptera). Teil 2. Entomologische Abhandlungen, 39 Suppl. ii+421 pp.
Wheeler, A.G. (2000). Plant bugs (Miridae) as plant pests. In: Schaefer, C.W. and Panizzi, A.R. (Eds.), Heteroptera of economic importance. CRC Press, pp. 37–83.
Wheeler, A.G. (2001). Biology of the plant bugs (Hemiptera: Miridae): pests, predators, opportunists. Cornell University Press, pp. 1–528.
