The Spanish Festoon Zerynthia rumina, a burst of spring colour

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Early spring sees the appearance in many arid parts of Catalonia of the smallest and most brightly coloured of all our Papilionidae, the Spanish Festoon Zerynthia rumina. This unmistakable butterfly is closely tied to the birthwort Aristolochia pistolochia, a calcicole plant that is the sole food plant of the species’ larvae. Although historically the Spanish Festoon has often been thought of as a rare butterfly, it has been recorded from most Catalan comarques and even from some typically Pyrenean areas. Nevertheless, its population densities are generally quite low and its flight period is relatively short and in
many sites this species has disappeared completely by mid-May.

Geographical distribution and situation in the CBMS

The Spanish Festoon Z. rumina is only found in north-west Africa, the Iberian Peninsula and southeast France(1). In much of its range in France, it coexists with the Southern Festoon Z. polyxena, a similar species that completely replaces the Spanish Festoon in south-east Europe(2). The Spanish Festoon is widespread in the Iberian Peninsula and has been recorded from all mainland Spanish provinces except Asturias, Vizcaya and Guipúscoa(3); it is absent only from the most northerly part of the Peninsula (that includes the highest mountains of the Pyrenees) and the Balearic Islands. In Catalonia it is one of the few species
whose range has been accurately studied (4,5). Despite living in localised and often small populations, it flies over much of the country and in 32 out of 41 comarques and with further searching it may even appear in other areas. Its distribution map suggests that it prefers low-lying areas of the coastal and pre-coastal mountains, but it also flies in much of the pre-Pyrenees and large areas of the Ebro Depression. In general this butterfly is closely tied to arid environments and avoids humid areas or
high mountains. Within the CBMS network the Spanish Festoon has appeared to date in 20 of the 76 Catalan stations (fig. 1). The greatest population densities occur in the Massif del Garraf and along the valley of the river Llobregat (for example, Sallent and
Gironella). In the mountains of Montmell and Prades, as well as in various sites in the Ebro Depression, populations are of intermediate density, while in the rest of the stations it is a rare species or is totally absent.

Habitats and food-plants

The Spanish Festoon is typically found in arid environments and in generally open and sunny and preferably calcareous habitats from sea level to midaltitude mountains up to 1,000 m (ref. 4). Data from the CBMS allows us to establish precisely which plant communities the species prefers (table 1). Using only data from sections in which the Spanish Festoon has an annual density
of over 0.1 individuals/100 m (thereby excluding observations of isolated or dispersing individuals) and taking into account only those plant communities with a section coverage of 30% or more, this butterfly is associated above all with dry false brome Brachypodium phoenicoides grassland (37% of sections) and calcareous Brachypodium retusum grassland (23% of the sections). The false brome grassland is the preferred habitat in sub-humid areas (for example, in the pre-Pyrenees and more inland mountain ranges), whilst Brachypodium retusum grassland is more often the chosen habitat in areas of semi-arid climate (Ebro Depression and some areas of the Garraf mountains). Less commonly, the Spanish Festoon is found in scrub dominated by rosemary Rosmarinus officinalis, thyme Thymus spp. and blue aphyllanthes Aphyllantes monspeliensis, in communities dominated by annual plants and Ampelodesma mauritanica or in other plant communities typical of low-lying calcareous areas. This close association with specific habitats can be explained by the monophagous nature of the species and the all but total dependence of Catalan populations on the birthwort Aristolochia pistolochia, a calcicole plant that appears in scrub under 1,200 m a.s.l. (ref. 6). Exceptionally, populations of Spanish Festoon appear in siliceous areas where A. pistolochia is not present (for example, in a few areas in L’Alt Empordà) ; it is possible that here the food plant is another birthwort, Aristolochia longa, a calcifuge species that is the preferred food plant in some populations in the south of the Iberian Peninsula (7). The bibliography also cites A. rotunda as a food plant in some European populations of the Spanish Festoon(1), although there is nothing to confirm this fact in Catalonia. Phenology and biological cycle The Spanish Festoon is a monovoltine butterfly that flies only in spring (fig. 2). Aside from areas of the pre-Pyrenees, where a few festoons are still on the wing in June, its flight period is restricted to the months of March, April and May. In the Ebro Depression and Garraf mountains the first butterflies are seen in the first weeks of March (and even at the end of February ; fig. 2a and b), whereas in more northerly locations (for example, Bages and El Berguedà) it is rare to see the species before the beginning of April (fig. 2c). In these latter areas the flight period is more compact than in the east of Catalonia, where emergence dates are more irregular. This is due possibly to the fact that in more continental areas the climate at the end of winter is more variable and depending on the
year the single annual generation of the festoon may be advanced or delayed. Even so, the averagedout data for all the years of the CBMS programme indicate that the maximum abundance of the species coincides in the three geographical areas shown in
figure 2 in the second half of April. As of yet, no evidence of a second summer-autumn generation has been found in Catalonia, as occurs in certain areas of the Iberian Peninsula (8) and Morocco (9) where A. pistolochia flowers for a lot longer. During the flight period, females festoons generally lay their eggs on the backs of leaves or on the flowers of A. pistolochia and only sometimes on the topside of leaves or on flower stalks. The eggs, laid in clusters one-by-one or occasionally in groups of two or three, are shiny white, just under 1 mm in diameter, almost round, smooth and without any type of relief. The caterpillars hatch in about two weeks and customarily hide inside the flowers by making a hole at the base of the inflated corolla tube (10). The caterpillars are not very mobile and once they have grown they are easy to find on the stalks and leaves of the host plant. They are characteristically yellow or brown-red, with a series of short black lines and 4-6 spines on each segment. The larval stage lasts for around six weeks and finishes as the host plants begin to die. The butterfly winters as a chrysalis and – at least in captivity - it is not unusual for two winters to pass before the adult butterfly emerges (11). We have no information as to whether this is habitual in natural populations.

Population tendencies

Due to pressure from collectors and the loss of habitat, three decades ago the Spanish Festoon was included in the first Red Data Book of Spanish Lepidopters (12). Nevertheless, more recent analyses show that the species’ populations are in fact stable (13) and in Catalonia, without ever being anywhere abundant, it is widespread and found in a great number of sites and cannot be thought of as under threat. Nevertheless, some populations occupy very small, well-defined sites and so may be threatened
more than other species by the alteration and destruction of habitat or even by collection. It seems that La Serra de Collserola is possibly the only site in Catalonia from which this species is documented as having disappeared (4). Albeit only on a short timescale, it is worth pointing out that no CBMS station has shown either positive or negative tendencies in its populations of Spanish Festoon. At local scale, oscillations may well be determined by the impact of a specific parasitoid, the icneumonid
wasp, Agrypon polyxenae, which attacks the larvae and then emerges from the chrysalis (14). Nevertheless, this affirmation needs to be tested as no data regarding parasitism in Catalonia exists.

Constantí Stefanescu

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1 Tolman, T. & Lewington, R., 2002. Guía de las mariposas de España y Europa. 320 pàg. + 104 pl. Lynx Edicions, Bellaterra.

2 Kudrna, O., 2002. “The distribution Atlas of European butterflies”. Oedippus, 20: 1-342.

3 García-Barros, E., Munguira, M. L., Martín Cano, J., Romo Benito, H., Garcia-Pereira, P. & Maravalhas, E. S., 2004. “Atlas de las mariposas diurnas de la Península Ibérica e islas Baleares (Lepidoptera: Papilionoidea & Hesperioidea) ”. Monografías Soc.
ent. aragon., 11: 1-228.

4 Viader, J., 1992. “Papallones de Catalunya. Zerynthia rumina (Linnaeus, 1758)”. Butll. Soc. Cat. Lep., 69: 40-52.

5 Viader, J., 1993. “Noves dades sobre Zerynthia rumina (Linnaeus, 1758) a Catalunya”. Butll. Soc. Cat. Lep., 71: 71-72.

6 Bolòs, O. de & Vigo, J., 1984. Flora dels Països Catalans. 736 pàg. Editorial Barcino, Barcelona.

7 Jordano, D. & Gomariz, G., 1994. “Variation in phenology and nutritional quality between host plants and its effect on larval performance in a specialist butterfly, Zerynthia rumina”. Entomol. exp. appl., 71: 271-277.

8 Olivares Villegas, J., Jiménez Gómez, J.L. & Yáñez, J., 1991. “Variations saisonnières de Zerynthia rumina Linné dans le sud de l’Espagne (Lepidoptera Papilionidae)”. Linn. Belgica, 13: 51-61.

9 Mokhles, A., 1984. “Calendrier des périodes de vol des Rhopalocères du Marroc”. Nota lepid., 7: 257-263.

10 Nyst, R.H. & Acquier, J.-Cl., 1984. “Nouvelles observations concernant Zerynthia polyxena Geyer et rumina L. (Lép. Papilionidae)”. Alexanor, 13: 239-240.

11 Nel, J., 1991. “Sur la plasticité écologique et la biologie de quelques Lépidoptères (Rhopalocera) du sud-est méditerranéen de la France (première partie)”. Linn. Belgica, 13: 159-220.

12 Viedma, M.G. de & Gómez Bustillo, M.R., 1976. Libro rojo de los lepidópteros ibéricos. 120 pàg. ICONA, Madrid.

13 Van Swaay, C. A. M. & Warren, M. S., 1999. Red Data Book of European Butterflies (Rhopalocera). Nature and Environment, 99: 1-260. Council of Europe Publishing, Estrasburg.

14 Shaw, M.R., Stefanescu, C. & van Nouhuys, S., en prep. “Parasitism of European butterflies (Hesperioidea and Papilionoidea)”.

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Fig. 1. Relative abundance of the Spanish Festoon Zerynthia rumina (expressed as the value of the annual index /100 m) in the different stations of the CBMS network (1994-2005).

Fig. 2. Phenology the Spanish Festoon Zerynthia rumina in (a) the Ebro Depression (data from five stations: Timoneda d’Alfés, Mas de Melons, Granja d’Escarp, Aiguabarreig and Sebes), (b) Garraf (data from two stations: Vallgrassa and Olesa de Bonesvalls), and (c) Llobregat valley (data from two stations: Sallent and Gironella).

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Taula 1. Dominant plant communities in the sections of the different CBMS itineraries in which the Spanish Festoon Zerynthia rumina attains population densities of over 0.1 exemplars/100 m.

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Photos. (a) Eggs nearly to hatch; (b) last instar larva; (c) pupa; and (d) adult of Zerynthia rumina (photographs: J. R. Salas).

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