Observations on a Swallowtail Butterfly, Papilio machaon L. in Ipswich, 2004.

STURMIA BELLA

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Observations on a Swallowtail Butterfly, Papilio machaon L. in Ipswich, 2004.

On 8 October 2004 I was asked by Rob Parker, the Suffolk Butterfly Recorder, to visit a garden in Woodbridge Road, Ipswich. The resident, Len Partridge, had reported a Swallowtail caterpillar on the one plant of Fennel, Foeniculum vulgare Mill., growing in his back garden. (Plate 9) Despite the late hour and overcast weather I was able to closely examine the caterpillar and take several close-up photos. It was subsequently examined by Rob Parker but it didn’t survive, possibly because of the late date and a fall from the plant onto the concrete path. Rob Parker noted the caterpillar was lethargic but hadn’t been parasitised. He also noted more Fennel in a neighbouring garden.

This late date for the caterpillar is similar to that recorded and photographed on Garden Rue, Ruta graveolens, in a garden on Westerfield Road, Ipswich, the date being 28 September 1998. Another Swallowtail caterpillar was recorded in 1998 from Nacton, first identified in late August, feeding on Choisya. (Stewart, 1999) These two caterpillars followed a series of eight Swallowtail sightings in Ipswich during 1998, probably the result of clandestine breeding and releasing on the Rivers Estate, Ipswich.

The 2004 caterpillar was preceded by four records of a Swallowtail butterfly in Ipswich. Three on the same day, 4 August, came from Pat Gondris in St Edmund’s Road, my own garden at Westerfield Road and from Iris Maeers in Sidegate Lane, though she expressed slight identification doubts because of a lack of tails. Ray Read also recorded one in Woodbridge Road, some time during the first week of August.

It is impossible to tell whether this was a genuine migrant or a local clandestine release and it is also not possible to ascertain if it was the continental species, Papilio machaon subsp. gorganus, or the British Swallowtail, subsp. britannicus Seitz. The nearest viable colony of the latter is at Strumpshaw Fen in the Yare valley, approximately forty miles from Ipswich. The three larval food plants mentioned would strongly suggest the continental species, P. m. gorganus, which has a catholic choice for egglaying. However, although many textbooks echo West (1993) who states that Milk Parsley, Peucedanum palustre, is ‘the only foodplant used’, other sources suggest that britannicus Seitz can use other larval food plants. Maitland Emmet and Heath (1990) state that eggs are also laid’ according Frohawk (1934) occasionally also on Wild Angelica (Angelica sylvestris). However, eggs laid on other umbellifers are usually those of second generation adults.

Peucedanum is often dying back in August when these late butterflies are on the wing’. In captivity ‘the larvae will feed on Garden Fennel, Foeniculum vulgare, cultivated carrot, parsley, parsnip and on Hemlock (Conium maculatum) and Angelica sylvestris. They will probably feed on other umbelliferous plants as they do on the Continent. A garden shrub, Choisya ternata, has also proved an ‘alternative’. (Cribb, 1983). A third source of alternative larval food plants was in a letter dated 4 February 2005 from the Site Manager at the R.S.P.B. Strumpshaw Fen reserve (Tim Strudwick, pers. comm.):

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‘I know that there have been sporadic records of eggs found on Angelica, but not in the last eight years that I have been at Strumpshaw. Since 2001, we have found eggs and larvae on hemlock annually across the river at Surlingham.

These are in a clearly defined area some distance from the nearest milk parsley. The larvae seem to grow to full size, and since egg laying has persisted in this area annually, I would assume that that they are pupating successfully. We have looked for larvae on hemlock elsewhere on the site without success…..I have not heard of swallowtails laying on meadow rue or any other non-umbelliferous species’.

It is unlikely that any Swallowtail seen in Ipswich or the rest of the county will be conclusively identified as P. m. gorganus or subspecies britannicus Seitz since Mendel and Piotrowski (1986) conclude that ‘Even preserved specimens can be difficult to assign, as distinguishing characters overlap’.

References Cribb, P. W. (1983). Breeding the British butterflies. Amateur Entomologists’ Society, Brentwood.

Maitland-Emmet, A. & Heath, J. (1990). The moths and butterflies of Great Britain and Ireland 7 (1). Colchester: Harley Books.

Mendel, H. & Piotrowski, S. H. (1986). The butterflies of Suffolk. Ipswich: Suffolk Naturalists’ Society.

Stewart, R. G. (1999) Observations on the Swallowtail Butterfly, Papilio machaon L. in Suffolk 1998. Trans. Suffolk Nat. Soc. 35: 98–100.

West, I. (1993). The swallowtail butterfly. Butterfly Conservation, Dedham, Essex.

Richard Stewart ‘Valezina’ 112 Westerfield Road Ipswich IP4 2XW

Trans. Suffolk Nat. Soc. 41 (2005)

R. G. Stewart Plate 9: Caterpillar of the Swallowtail butterfly (Papilio machaon) feeding on Fennel (Foeniculum vulgare) in a garden in Ipswich, 2004 (p. 69).