The Spinose Skipper, Favria cribrellum (Eversmann, 1841) [formerly in Muschampia] is considered to be a very localised species in Eastern Europe occurring in only a small number of isolated colonies. Its ecology, especially relating to its host plant, has long remained unknown. Only in the last decade of research has more light been shed on the distribution and habitat requirements of this species in its western range. The host plant of the Spinose Skipper in the Republic of North Macedonia is revealed for the first time. Three eggs and three larvae were discovered in 2017 on a species of Potentilla, tentatively identified as P. detommasii, from a site near Govrlevo, SW of Skopje. The choice of a cinquefoil as a hostplant provides new evidence to support the species recent separation from the genus Muschampia.

Favria cribrellum (Eversmann 1841), formerly placed in Muschampia Tutt, [1906] or the Spinose Skipper, is a rare and very localised hesperid species in Europe. It is recorded from several countries in Eastern Europe: Serbia (Dincǎ at al. 2010; Popović and Đurić 2014; Langourov 2019), the Republic of North Macedonia (Schaider and Jakšić 1989; Verovnik and Micevski 2009; Dincǎ et al. 2010; Davkov and Mérit 2018), Bulgaria (Kolev 2003; Dincǎ et al. 2010; Hoejgaard and Beshkov 2011; Langourov 2019; Wagner and Kolev 2019), Romania (Rákosy et al. 1997; Székely 2008), Ukraine (Nekrutenko and Tshikolovets 2005; Tshikolovets 2009, 2011), Russia (Southern Urals) (Eversmann 1841; Tshikolovets 2009, 2011) and more recently from Greece (Davkov and Mérit 2017, 2018). From Hungary no records have been confirmed; reports are most likely due to confusion with older records from Western Romania, once part of the Austro-Hungarian Empire, and at present the species should not be considered as a member of the butterfly fauna of this country (Dincǎ et al. 2010). It is estimated that the Spinose Skipper is present in only 30 sites across its European range (Dincǎ et al. 2010; Davkov and Mérit 2018) and has been designated a status of NT (Near Threatened) in the European Red List of Butterflies (van Swaay et al. 2010).

Outside Europe, F. cribrellum inhabits a large area stretching from Russia (Altai, Siberia, Amur), Kazakhstan, all the way to Mongolia and Northern China (Tolman and Lewington 1997; Gorbunov 2001; Tshikolovets 2009, 2011), however, it is considered an uncommon and localised species. There has been much speculation regarding the choice of host plant of the Spinose Skipper. Several papers have been published during the last decade shedding light on the distribution and habitat requirements of this species in the western part of its range (Dincǎ et al. 2010; Davkov and Mérit 2018). Many authors have suggested a cinquefoil (Potentilla L.) species as the potential host plant (Rothschild 1914; Higgins and Riley 1980; Chinery 1989; Korshunov and Gorbunov 1995; Tolman and Lewington 1997; Gorbunov 2001; Nekrutenko and Tshikolovets 2005; Tshikolovets 2009, 2011; Dincǎ et al. 2010; Tshikolovets and Nekrutenko 2012). Davkov and Merit (2017, 2018) speculate that both Potentilla deorum Boiss. and Heldr and Potentilla kionaea Halácsy could be utilised as host plants by F. cribrellum in Greece. According to the observations of S. A. Andreev, in the Volga region (Tikhonov 2021) caterpillars develop on a species of Marrubium L. Finally, Wagner and Kolev (2019) discovered both eggs and larvae on Fragaria viridis Weston in the Sofia district of western Bulgaria.

During the period from 2014 to 2017 several field trips were conducted at a site near Govrlevo, SW of Skopje in the Republic of Northern Macedonia with the aim of unearthing the host plant of the Spinose Skipper. The locality was previously known to both authors as an area where healthy populations of the butterfly occurred. The first visits to the site were carried out between 9.v.2014 and 22.v.2014 by the second author. All other surveys were undertaken by the first author, the first one on 30.iii.2016, the second on 15.viii.2016, the third between 13–14.v.2017, the fourth on 2.vi.2017 and the last on 14.viii.2017. During their initial visits the authors concentrated on searching for plants of the Phlomis L. genus, but they also inspected the leaves of several Potentilla species found at the site. It wasn’t until 13.v.2017 that the host plant was discovered and three eggs collected. Several seedlings and a number of mature plants were dug up from the habitat at this time and placed in wet cloth in a plastic bag and kept moist until the end of the field trip. In addition, a quantity of soil from the habitat was taken in order to help nurture the relocated host plants. In total, 11 plants in different stages of development were removed from the site. The newly hatched larvae were placed onto plant seedlings. The roots of these seedlings were immersed in water in a plastic bottle, with a wad of cotton wool placed at the base to stop the young larvae from falling into the water. The upper part of the plant was covered with a plastic bottle, and some fine netting was placed over the opening to prevent the larvae from escaping, and to prevent potential predators from entering the container. The remaining plants were placed in water. All these plants reacted well to their new environment and started growing new roots in the first week. For the first two weeks the larvae were kept indoors under artificial light (for a 12-hour period) before being transferred onto potted plants. The pots were taken outside and kept in a sheltered, shady place. These plants, collected at the habitat in Govrlevo, had been transferred to black plastic pots, each 12 cm in diameter, and left in partial shade. Three, evenly spaced, wire hoops were inserted into the soil of each pot to form a framework over which a covering of fine netting was emplaced and secured to the rim of the pot using an elastic band. One larva was placed in each pot.

A detailed description of the larval morphology and the development stages of the Spinose Skipper is not given in this paper since Wagner and Kolev (2019) already presented a very accurate account of the preimaginal stages, and our observations, in the main, concur with their description. However, contrary to the finding of Wagner and Kolev (2019) who state that the L1 larva “creates a typical Muschampia shelter by cutting half of the leaflet width circularly and folding this part to the other side”, FF noted that the L1 larvae did not construct any shelter and remained on the tip of the leaves feeding on small amounts of leaves, leaving the cuticule intact. The first shelter was constructed at L2 stage at which time he witnessed a larva folding two leaves together. It is worth noting that both groups of authors observed the caterpillars entering a summer diapause. While visiting the habitat in the Republic of North Macedonia during August, the first author noted that the host plants had entered a summer dormancy to avoid desiccation, hence making them unsuitable for larval development. Both authors unsuccessfully attempted to induce the larvae to bypass a winter diapause by exposing them to constant light during the later stages of their larval development, confirming the species is undisputedly univoltine. However, the most interesting observation relates to the species host plant. At the time of egg sampling, the information regarding the host plant in Bulgaria published by Wagner and Kolev (2019) was not available to MGP and FF, and a wide range of plants were treated as possible host plant candidates. After observing females laying eggs, a plant sample was collected and presented to the Faculty of Biology, University of Belgrade, where it has been provisionally identified by Professor Gordana Tomović as Potentilla detommasii Ten. (Fig. 17). Taking into consideration the choice of host plant of the Spinose Skipper, it is worth noting that all species from the Western Palaeartic region that were considered to be in the Muschampia genus, prior to the recent taxonomic rearrangment (Zhang et al 2020) were known to feed on plants from the genus Phlomis: M. proto (Ochsenheimer, 1816) on Phlomis crinita Cav., P. bovei De Noé, P. fruticosa L., P. lychnitis L., P. herba-venti L. and P. pungens Willd.; M. alta (Schwingenschuss, 1942) on P. fruticosa; M. proteides (Wagner, 1929) on P. brachyodon (Boiss.) Zohary ex Rech.f., P. kurdica Rech.f. and P. chrysophylla Boiss.; M. mohammed (Oberthür, 1887) on P. crinita and P. bovei; M. tessellum (Hübner, 1803) on P. samia L., P. tuberosa (L.) Moench. and P. pungens; while the host plant of M. leuzeae (Oberthür, 1881) is believed to be a species of Phlomis (Tolman and Lewington 1997; Benyamini and Avni 2001; Tshikolovets 2011, Hinojosa et al. 2021). Similarly, all other species of the Muschampia genus prior to the recent taxonomic changes, that have a documented lifecycle, use plants of the genus Phlomis (Dincǎ et al. 2010). Consequently, and understandably, it was assumed that the Spinose Skipper would also utilise Phlomis as its larval host plant. However, having observed ovipositing on a cinquefoil species and, having taken into consideration the information published by Wagner and Kolev (2019), regarding the development of larvae in Bulgaria on Fragaria viridis, it can be concluded that the choice of host plant (Tribe Potentilleae) differs substantially from that of the Muschampia genus sensu stricto (prior to Zhang et al 2020) which utilise plants of the genus Phlomis or Muschampia sensu lato (after Zhang et al. 2020), mostly plants from the Lamiaceae family. Using nuclear and mitochondrial DNA data, Zhang et al. (2020) found that M. cribrellum is not monophyletic with the genus Muschampia and thus is best assigned to the monotypic genus Favria Tutt, 1906, which is sister to the genus Gomalia Moore, 1879. Interestingly, representatives of the genus Gomalia are morphologically very different, when compared to Favria, particularly the egg and larval stages, as is their choice of Abutilon Mill. species (Malvaceae) as host plants (Benyamini 1990; Cock 2016). Finally, in light of the currently available data, Wiemers et al. (2020) proposed changing Muschampia cribrellum to Favria cribrellum as was used in the current taxonomic checklist of European Butterflies (Wiemers et al. 2018).

Figures 1–17. 

Favria cribrellum from Suva Planina, Republic of North Macedonia: 1. Habitat at Govrlevo, 19.v.2014; 2. Adult female, 26.v.2014; 3. Adult male, 20.v.2014; 4. Young host plant in its habitat; 5. Ovum, 28.v.2014; 6. L₁ larva, 24.v.2017; 7. L₂ larva, 3.vi.2017; 8. L₂ larva in shelter, 3.vi.2017; 9. L₃ larva, 27.vi.2017; 10. L₃ larva, close-up up of mouth parts, 27.vi.2017; 11. L₄ larva, 12.ix.2017; 12. L₄ larva, 27.x.2017; 13. L₄ larva in silken tent, 28.x.2017; 14. L₅ larva, close-up of head, 29.iv.2018; 15. L₅ larva, 29.iv.2018; 16. Pupa, 8.v.2018; 17. Potentilla detommasii in its habitat, 20.v.2014. – Photographs by F. Franeta and M. Gascoigne-Pees.

The host plant of the Spinose Skipper in the Republic of North Macedonia is a cinquefoil species. Several other species of cinquefoils were recorded at the site near Skopje. However, it was evident that the butterfly only utilises one species for oviposition. This plant species was growing in the driest parts of its habitat, in some places in large groups and in other situations as individual specimens. All three eggs were found on seedlings, each with six to eight leaves. After several field trips and rearing attempts, the authors have proved conclusively that the host plant of F. cribrellum, in the Republic of North Macedonia, belongs to the genus Potentilla, tentatively identified as Potentilla detommasii. This information, coupled with the data presented by Wagner and Kolev (2019) on the lifecycle of the species in Bulgaria, puts an end to any long-established speculations regarding the host plant of the Spinose Skipper. It is likely that in other habitats throughout its range, the species utilises different Potentilla species or other plants from the tribe Potentilleae. The utilisation of a host plant from the tribe Potentilleae both in Bulgaria and in the Republic of North Macedonia supports the molecular differentiation of this species from the genus Muschampia, whose species with a known lifecycle feed almost exclusively on species of Lamiaceae.

The authors would like to thank Professor Gordana Tomović from the Faculty of Biology, University of Belgrade for helping identify the host plant. We also thank Professor Rudi Verovnik from the Faculty of Biology, University of Ljubljana for proof reading the text and for his useful comments and suggestions. In addition, an expression of gratitude is extended to Professor Branko Micevski and Nikola Micevski from Skopje for their companionship and invaluable help with field observations.