The Spanish Festoon Zerynthia rumina, a burst of spring colour

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
Peninsula7

?

. The bibliography also cites A. rotunda
as a food plant in some European populations of
the Spanish Festoon1

?

, 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 Peninsula8

?

and Morocco9

?

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,

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