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Posted by Jes

The Butterflies of the Maltese Islands & Species Focus: Maltese Race of the Swallowtail (Papilio machaon ssp melitensis) Eller 1936

Figure 1 Maltese race of European Swallowtail

Range: The European Swallowtail (Papilio machaon) is widespread in Europe having a range that includes the entire continent except for Denmark (extinct), Ireland, most of Britain and Northern Russia. Many subspecies and forms exist, including P.m. britannicus in Norfolk, England, and P.m. melitensis in the Maltese Islands. Interestingly from an Irish viewpoint, the European Swallowtail is currently breeding in parts of the South of England and may extend its range to Ireland with continued climate warming.

Distribution: There are seven Maltese islands in the Maltese archipelago and the swallowtail is found on the three main islands of Malta, Gozo and Comino. I found the butterfly throughout Gozo where I spent most time. I found it on streets, including on the main street of the local capital, Victoria, in gardens, scrubby areas, in the countryside at the edge of farmland, fallow land, steppes (grasslands), garrigue (low, scattered scrub on rocky ground, especially karst limestone), at Calypso’s Cave above the beautiful Ramla Bay, along roadsides in various parts of Gozo such as the villages of Ħondoq, Nadur, Xagħra (beside the windmill) and on Xlendi seafront. It is mainly seen singly, with two seen together on some occasions. The highest number I saw in one day was five. It is a wide-ranging nomadic species, rarely settling in any area for long.

Flight Period:

The butterfly is trivoltine (three generations) flying between February and November.

Description: The Maltese Swallowtail is a magnificent butterfly and much loved in Malta. It is commonly called the Queen’s butterfly (Farfett tar-Regina in Maltese) and also The Lira because the butterfly featured on the old Maltese lira stamp. Males and females look alike but females are somewhat larger. The wingspan is an impressive feature, frequently around 8 cm. The bright yellow, black-barred wings, the broad blue band on the hind wings and red spot at the tornal area as well as the elegant scalloped edges topped off with long smart velvet black tails edged with cream make this butterfly a delight to behold.

Behaviour: It is fond of nectaring on Clustered Carline-thistle (Carlina involucrata) and also flutters, briefly, around purplish-red flowers of Bougainvillea Creepers (a common garden plant in Malta). It is highly elusive, rarely settling for long; it often alights on flowers with wings held vertically over the body, often fluttering its wings as it feeds. Males feed less often than females; males scour feeding areas for females, flying low around areas with flowers. In the morning, the butterfly basks with wings held wide open before flight is attempted. Several pristine individuals were seen from mid-July suggesting that the second half of July may be early in the emergence period of the second brood. Soon individuals with a tail or both tails missing appeared; this is possibly the result of attack by ubiquitous sparrows deceived into thinking that the tail with the red eye mark close by is the butterfly’s head. The species is also a master of the skies, covering several kilometres at a time without pause. It climbs easily; I watched it fly from ground to the roof of a four storey building.

During very hot weather, hill-topping by males was observed; single males flew at tops of hills spending their time flying often directly into the wind or resting on vegetation. Hill-topping is a curious habit by some male butterflies. It involves males (and females?) of some species flying to the highest point in a locality and remaining there for several hours, perhaps days. On hill and cliff-tops the butterflies fly low over an area of high ground; fluttering, gliding and some vigorous patrolling was observed. Males also perched for short or longer periods (during windy conditions). One individual observed during very hot weather flew vigorously around a well defined area of about a hectare (observing boundaries formed by a hut, wall, burned strip and change in terrain height) flying about 60 cm above the ground following a regular flight path and settled briefly yet frequently on the two pieces of vegetation. Individuals were observed taking nectar but feeding appeared to be relatively unimportant.

Most Swallowtails observed hill-topping did not appear interested in establishing a territory or mate-seeking; they simply looked to be relaxing. Only once did I see two males in the same area and some territorial behaviour was seen with one driving the other off its patch. I noticed that the tendency to hill-top occurred mainly during very hot weather so the cooler, breezier conditions at altitude may be an incentive to hill-top.

During the hottest weather when temperatures reached over 30C I encountered males only at altitude. Perhaps this strategy serves a number of purposes; it may allow the butterfly to avoid over-heating and remain active. It may demonstrate to females that a hill-topping male is a worthy mate because he has the capability to reach the highest point. High points in a landscape may also be a suitable meeting point for species with a low population density. Studies show that males of some South American swallowtail species use hill-topping as a mate-seeking strategy.

However, it was not possible to determine whether the latter reason for hill-topping applies in the case of the Maltese Swallowtail as no females were observed on the hill tops. Most of the individuals looked pristine and it is possible that males use hill tops as places to rest while they mature. Perhaps a period of maturation must take place before males are able to breed, and hill tops provide a convenient place for the development of sexual maturity. Whatever the reason, the habit enabled me to obtain close views of this elegant butterfly.

Life History: Swallowtails lay their eggs singly on the larval host plant. At the end of July I observed a swallowtail lay a single egg low down on underside of a leaflet of an isolated, leafy Fennel plant (Foeniculum vulgare) growing in bare ground. The female approached the plant fluttering low and investigatively around the plant before alighting, curling its abdomen and depositing her egg. The freshly laid ovum is spherical, yellow and smooth.

Figure 2 Fully fed Swallowtail larva

Figure 3 Swallowtail pupa

After a week the egg turns dark grey-green and hatches. The grey-black larva consumes the entire egg shell and moves to the leaflet tips to feed. Despite its tiny size its dark colour means it is conspicuous on the host plant. The second in-star is 5 mm at first and is an interesting example of deception; with its white middle segments and mainly black elsewhere it looks like a bird dropping. The third stage which was reached at two weeks was similar in appearance but had 11 conspicuous orange markings on its spiracles (breathing holes), the third and fourth abdominal segments dorsally white and overall still mainly black in appearance. The fourth in-star larva is a handsome creature. The larva, now measuring 10 mm is now mainly bluish-green (deepening to light green during the fourth stage) with orange spiracular markings on all except the anal segment. Above the orange marking is a black, rear leaning marking, followed by a white space and a black spot except on abdominal segment four. A pair of black-tipped orange or yellow dorsal spikes rises from each segment. The border of each segment is outlined in black.

The final in-star (fifth stage) measures 20 mm initially. The fourth in-star larva remained static for two days before moulting. Its overall appearance is similar to the fourth stage but spines have almost disappeared by this stage, the markings look better defined and the head looks more prominent, being less tucked into the thorax. The head is green with black markings. This is the stage most often illustrated in books. Interestingly, the fifth in-star larva was observed to consume the cast skin (exuvia) minutes after moulting. No cast skins were found following previous moults so consumption of earlier cast skins may be presumed. The final stage larva is much more mobile than the earlier stages and ranges widely over the plant to feed, consuming large sections of leaves. Night feeding was observed. The fully grown larva (Fig 3) I studied measured 30 mm when hunched up and over 40 mm when extended; when fully extended it is probably about 50 mm. When fully fed the larva becomes restless, moving swiftly up and down the plant. Finally it settled low down on the main stem and attached itself by a silk pad (abdomen) and girdle (second abdominal segment) and pupated, head facing upwards, two-three days later. The length of the larval stage in captivity, which was 27 days, accords with the life span in the wild described in Heath et al 1990 for the British race, P.m. britannicus .

One unusual feature of the larva was the absence of the osmeterium. This is a fleshy, orange-coloured extendable organ concealed within the first thoracic segment of swallowtails which produces an offensive smell of rotten pineapple when erected. This is used to deter predators and appears when the larva is alarmed. The larva studied did not produce the organ even when agitated. The absence is unusual because the larva of the swallowtail found on the Maltese islands has this defence mechanism (Anthony Seguna, personal comment).

The pupa comes in two colour forms, green and pale brown. The studied larva produced a green pupa, (Fig 4) probably because green was the ambient colour. The pupa measured 30 mm, was wrinkled and rugged in appearance with yellow markings showing eight parallel yellow spots on the upper side of the abdomen and a single pair on the thorax upper side. The pupa probably lasts three weeks except when it over-winters. The adult butterfly lives for about three weeks.

Conservation Status of the Maltese Swallowtail: While some concerns have been raised about the population size of this endemic sub-species in recent years there appears to be little fear for its numbers at present. It is a mobile species that has no specific habitat needs aside from the presence of the larval host plant, which is found almost everywhere on the Maltese islands. Fennel is robust and drought resistant and provides nectar for the adult as well as food for the larva. (Rue (Ruta graveolens) is also used) The favourite source of nectar in July is the Clustered Carline-thistle and this plant is also common, especially on fallow land. There was some unnecessary planting of ‘ornamental’ flowers along some main roads where the natural vegetation was removed but this does not appear to be an extensive practice.

Conservation Status of Maltese Butterflies: According to Van Sway et al. 2010, European Red List of Butterflies, Malta has 18 butterfly species (the figure is probably inaccurate; Haahtela, T et al. 2011 states that Malta has 24 species).Sadly there are serious concerns about the grassland species. The Small Copper and Brown Argus are probably extinct. The Small Heath is recorded in the Millennium Atlas as declining in Malta by 15-25% in 25 years.

Geranium Bronze

Meadow Brown hyperhispulla form

Most alarming is the status of the Meadow Brown which exists as a unique form on Malta, as Maniola jurtina ssp hyperhispulla. The uppersurfaces of the wings of the female are adorned with a deep orange that extends to the chocolate-coloured submargins. The butterfly is appreciably larger than our Irish Meadow Brown, and the undersides are paler. Only a small number of sightings have been made in recent years. There are only seven records for Malta from 2001-2005 while in Gozo it is regarded as “slightly more numerous, with twos and threes sometimes encountered but apparently with very limited distribution” (Bonet and Attard 2005). This description of its occurrence on Gozo was reflected in my observations.  I saw four males near the coast at Dwejra (west Gozo) on 24/07/2014 and two males north of Ħondoq village (south-east Gozo) on 26/07/2014 and later, on 29/07/2014, two males and a female in the same location in a flower rich field. On 30/07/2014 I saw a male and female, separately, above the cliffs at Xlendi (south-west Gozo). I saw none elsewhere.

Interestingly these sightings were on semi-natural grassland which is scarce elsewhere due to the intensive farming being practiced. There is enormous pressure on the available land on these islands; Malta is the fourth most densely populated state on earth (1,317 people per km2). Farming of formerly wild land, with even narrow terraces on the limestone hills cultivated involving extensive use of pesticides means that little semi-natural grassland habitat remains. I cannot help feeling that the Maltese form of the Meadow Brown, possibly the most magnificent of the Meadow Browns found in Europe and until recent years described as very common, is on the brink of extinction. Urgent action is needed to protect grassland habitats.

Bath White

Lang's Short-tailed Blue

On a more positive note the Wall Brown was abundant; it was frequent near stone walls, on lanes, tracks and along the coast. The Geranium Bronze, a recent coloniser is common in gardens; I noticed egg laying on geraniums. Lang’s Short-tailed Blue is also common as is the Common Blue although I did not find the latter to be numerous anywhere.  The Painted Lady was numerous in flower rich coastal areas but Clouded Yellows were only encountered singly as was the Bath White. Small Whites which are found on the wing throughout the year were everywhere. Only a single Long-tailed Blue was found. It is large for a blue, perches briefly and is remarkably fast so I could not obtain a photograph. The same frustration was met with when I sighted a beautiful male Cleopatra, its deep orange and sulphur wings a real delight. Local butterfly enthusiast Anthony Seguna informed me that July (during my stay on Malta) is not the optimum month to seek butterflies and the constant heat and drought during high summer makes this unsurprising. Never-the-less the experience was enjoyable and I recommend a visit to the Maltese islands in May/June to anyone who enjoys rambling along the many coastal walks where the best habitats and best views are found. A fascinating history is an added attraction along with the values of the Maltese people. Where else in the European Union can you routinely see car keys left in the ignition, with the windows left down, all night?

Cliffs at Xlendi showing garrigue habitat.

References

Asher, J., Warren, M., Fox, R., Harding, P., Jeffcoate, G. and Jeffcoate, S. (2001) The Millennium Atlas of Butterflies in Britain and Ireland. Oxford University Press, Oxford.

Attard, J and Bonett, G. (2005) The Maltese Countryside Volume 2. Publishers Enterprises Group, Malta.

Emmet, A.M. and Heath, J. (eds) (1990) The Butterflies of Great Britain and Ireland. 7(2). Harley Books, Colchester.

Haahtela, T et al. (2011) The Butterflies of Britain and Europe. A and C Black, London.

Tolman, T. and Lewington, R. (2009) Collins Butterfly Guide. Harper Collins. London.

Weber, C.W. and Kendzior, B. (2006) Flora of the Maltese Islands A Field Guide. Margraf Publishers, Marburg.

All photographs copyright J.Harding.