© Norwegian Journal of Entomology. 24 June 2020 The firebug Pyrrhocoris apterus (Linnaeus, 1758) (Hemiptera, Heteroptera) new to the Norwegian fauna – with an explosive expansion in Northern Europe ANDERS ENDRESTØL & STEFFEN ROTH Endrestøl, A. & Roth, S. 2020. The firebug Pyrrhocoris apterus (Linnaeus, 1758) (Hemiptera, Heteroptera) new to the Norwegian fauna – with an explosive expansion in Northern Europe. Norwegian Journal of Entomology 67, 81–90. The Firebug Pyrrhocoris apterus (Linnaeus, 1758) (Hemiptera, Heteroptera) is presented new to the Norwegian fauna. Several hundred individuals were observed in a residential area in southeast Norway, centred around two Tilia trees. P. apterus has had an explosive expansion in Northern Europe the recent years, and its range expansion and means of expansion is discussed. Key words: Hemiptera, Heteroptera, Pyrrhocoridae, Pyrrhocoris apterus, Norway, Northern Europe, range expansion. Anders Endrestøl, Norwegian Institute for Nature Research, Sognsveien 68, NO-0855 Oslo, Norway. E-mail: [email protected] Steffen Roth, University Museum of Bergen, Department of Natural History, P.O.Box 7800, NO-5020 Bergen. Email: [email protected] Introduction coridae) is an example of a true bug that has expanded its range northwards the last decades There are about 470 species of Heteroptera (Voigt 2004, Tolsgaard 2005). Pyrrhocoridae registered in Norway (Ødegaard & Endrestøl Amyot & Serville, 1843 contains about 30 genera 2015). Some of these have become established and 300 species worldwide, with 13 genera and 43 or introduced in Norway the recent years, either species present in the Palearctic Region (Kerzhner as a result of natural range expansion or human 2001). The genus Pyrrhocoris Fallén, 1814 is activity (e.g. Ødegaard & Endrestøl 2007, represented with six species in the Palearctic Staverløkk et al. 2009, Mjøs et al. 2010, Ødegaard (Kerzhner 2001). Since P. apterus is easily bred 2014, Olsen et al. 2017). Many of the human in laboratory condition, its use as an experimental induced introductions of alien insects into Norway tool for biological research is extensive (review and other countries in Europe are a result of trade in Soucha 1993), even research on personality with ornamental plants (e.g. Smith et al. 2007, (Gyuris et al. 2010). Westergaard et al. 2020, Sandvik et al. 2020). We here present P. apterus new to the Many species of true bugs have also been reported Norwegian fauna. This represents not only a new to change their distribution range in general, species to Norway, but also a new family of true presumably due to a warmer climate (see review bug to Norway; Pyrrhocoridae. We also present in Musolin & Fujisaki 2006). data on, and discuss, its range expansion in Pyrrhocoris apterus (Linnaeus, 1758) (Pyrrho- Northern Europe. 81 Endrestøl & Roth: Pyrrhocoris apterus new to the Norwegian fauna The records Several other garden plants and bushes were present around the locality, and a linden hedge The species was first observed by M. Grandahl in (Tilia) (with hawthorn (Crataegus) in between) a garden in a residential area in Sarpsborg, Viken was surrounding the garden. The hedge was more 18. April 2020. Photos where sent to the second than 100 m long, but no individuals of P. apterus author who identified them as P. apterus. Later, seemed to be dwelling on or under this hedge. the first author went to the locality and confirmed The hedge was presumably planted there in the the presence of the species. mid 1970-ies (M. Grandahl pers. com). Several Ø (Viken), Sarpsborg: Klokkerskogen (11. clusters of individuals were found under a bush 18188, 59.25274), 18.IV.2020, 2 ex., leg. M. of Philadelphus coronaries, a few meters from the Grandahl, det. S. Roth; 23.IV.2020, 11♀♀ (brac.) two Tilia trees. 12♂♂ (brac.) 2♂♂ (macr.), leg./det. A. Endrestøl, One record of P. apterus is published on Gbif. coll. Norwegian institute for nature reseach org (2020) from Norway (via naturgucker.de) (NINA) / University Museum of Bergen (UMB); from Innlandet county, Sør-Fron municipality, 25.IV.2020, 5 ex. leg./coll. T.J. Olsen; 27.IV.2020, Gålå 12. July 2018. We expect that to be erroneous 1♀ (brac.) 1♂ (brac.), leg. M. Grandahl, coll. (probably Corizus hyoscyami (Linnaeus, 1758)), NINA; 30.IV.2020, 3♀♀ (brac.) 2♂♂ (brac.) as this is more than 900 m a.s.l., and no Tilia 2♂♂ (macr.), leg. A. Endrestøl, coll. NINA. can be found in the area. This record is thus not From the 34 individuals investigated by the considered. The closest known record from the first author, 30 of the individuals were brachypter new Norwegian population is in Munkedal, (brac. – short-winged) and four of the male Sweden, some 85 km southeast of Klokkerskogen. specimens were macropter (macr. – long-winged). The body size of a pair in copula with an apparent size difference were measured to 7,5 mm (♂) and The species 10,3 mm (♀) (Figure 1c). The species had never been observed in Pyrrhocoris apterus is a very conspicuous the area before, and there were several hundred species, strikingly colored in black and red individuals aggregated there at the time of the (aposematism) (Figure 1). The coloration is first observation. The species was observed somewhat variable (Soucha 1993), and several several times the following days, and the number forms are described (Kerzhner 2001). The species of individuals seemed to decrease (M. Grandahl is given as 9,0 –11,5 mm by Wachmann et al. pers. com). On the 23. April 2020 there were still (2007), and 6,5 –12 mm by Soucha (1993). In probably several hundred individuals present, more Norway it can only be confused with the widely scattered and in smaller aggregates (Figure 1a,b). distributed Corizus hyoscyami (Rhopalidae), but The main population seemed to be distributed the markings are different and ocelli are lacking in an area of about 50 m2, extending to 120 m2 in Pyrrhocoridae (P. apterus). In southern Europe when counting single individuals. After some cold P. apterus could easily be confused with a very days at the end of April, most individuals seemed similar species, Scantius aegyptius (Linnaeus, to have vanished at the 30. April (A. Endrestøl 1758) (Pyrrhocoridae), most easily separated by pers. obs.), and some where later seen burrowing the color of the abdominal sternites (Mata et al. themselves down into the sand (M. Grandahl pers. 2013). Other members of the genus Pyrrhocoris com.). are in general colored in black or brown (Voigt The population was centred around two trees 2004), except P. sibiricus Kuschakewitsch, 1866, (Tilia cordata) (Figure 1d), to a large part on the which is also colored in black and red, but much ground. The ground around the trees was slightly duller compared to P. apterus. Finally, several sloped towards southeast, consisting of a lawn species of Lygaeidae from Central Europe are also with grasses, moss and non-vegetated spots of conspicuously coloured in red and black, but they sand, and some debris of leaves and Tilia seeds. also have ocelli as opposed to Pyrrhocoridae. 82 Norwegian Journal of Entomology 67, 81–90 (2020) a b c d e FIGURE 1. a,b. Aggregations of Pyrrhocoris apterus from Sarpsborg, Norway 23. April 2020. c. A pair of P. apterus in copula (♂:7,5 mm, ♀: 10,3 mm). d. The locality of P. apterus from Klokkerskogen, Sarpsborg, where the majority of individuals were observed under the two Tilia trees. e. P. apterus on the trunk of a Tilia tree. Photos: Anders Endrestøl, NINA. 83 Endrestøl & Roth: Pyrrhocoris apterus new to the Norwegian fauna Another strikingly feature with this species (Fabaceae) (Wachmann et al. 2007) and even on is that it aggregates in large groups as a result of spruces Picea (Spuris 1995). In Europe, Tilia aggregation pheromones and contact pheromones is the most common food source and P. apterus (Wachmann et al. 2007). They also have alert therefore tends to cluster under linden trees, which pheromones that results in an alarm response that coincides with observations on the Norwegian quickly can dissolve aggregations (Soucha 1993, locality reported here. They are adapted to an Wachmann et al. 2007). extremely dry diet of ripe seeds (Soucha 1993). The species lives on various Malvaceae such To some extent they might also be zoophagous, as Tilia, Hibiscus, Malva, Alcea, Althaea and necrophagous and cannibalistic (Soucha 1993, Lavatera (Voigt 2004). They can also be found on Wachmann et al. 2007). This form of polyphagy and around other trees, eg. Robinia pseudacacia is according to Soucha (1993) one of the reasons FIGURE 2. Map of Pyrrhocoris apterus (Linnaeus, 1758) in Northern Europe from 1960 to 2020. Records prior to 1960 are not considered. Green dot is the record presented here. Source: Gbif.org (2020), Fugleognatur (2020), ArtPortalen (2020), FinBif (2020), Dabas Dati (2020), eElurikkus (2020). 84 Norwegian Journal of Entomology 67, 81–90 (2020) the species is widespread and expanding its range. According to Wachmann et al. (2007) the species overwinters as adults under moss, loose bark or leaves. That is in accordance with the observation of adults in mid-April in Norway. The females start to lay eggs in May, and can continue to lay eggs for a longer period (Voigt 2004, Wachmann et al. 2007). One brachypterous female lays about 383 eggs, but with substantial variation (± 208 eggs) (Soucha 2013). The lifespans and total number of eggs laid by females of the two wing morphs do not differ significantly, even though such a difference is found in several other insect-species with wing dimorphism (Soucha 2013 and references therein). Eggs are laid in the FIGURE 3. Number of records (one record per ground (Voigt 2004), and females makes small locality) per year of Pyrrhocoris apterus (Linnaeus, pits in the ground where she lays the eggs before 1758) in total in Norway, Sweden, Finland, Estonia, covering them (Soucha 1993).