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The Wormwood Moonshiner Amara fusca

 

Wormwood Moonshiner

Amara fusca is a rare Breckland beetle feeding on the seeds of a rare Breckland plant Field Wormwood Artemisia campestris. Both plant and beetle are also recorded from Crymlyn Burrows on the Glamorganshire coast which strongly suggests that the Glamorganshire populations of Artemisia campestris have been wrongly regarded as alien. The beetle is a BAP priority species so it should be searched for at Crymlyn Burrows and other past or present sites for Artemisia campestris.

Background to the beetle

Amara fusca was discovered at the Wangford roadside, West Suffolk (TL756836, VC26) on 6th September 1993 (Telfer and Eversham, 1994). Prior to this discovery, the species had not been seen in Britain since 1942 (a single specimen at Swanley, West Kent) and all previous records appear to be prior to 1900.

Amara fusca is a member of the ground beetle family (Carabidae) and like others in the genus Amara, is a broadly-oval, rather slow-paced, seed-feeding species. A. fusca is a medium-sized unmetallic brown Amara with pale antennae, superficially similar to A. apricaria and A. equestris amongst others. The 1993 discovery was the first record of A. fusca for the Breckland area, which is a hotspot for seed-feeding carabids in the genera Amara, Harpalus, Ophonus and Bradycellus.

A. fusca was given Endangered (RDB1) status by Hyman and Parsons (1992) and was added to the list of UKBAP Priority species in August 2007, at which time it was also christened the ‘Wormwood Moonshiner’.

Wormwood Moonshiner

Moonshining on some Wormwood © John Walters

An old vernacular name for certain beetles is ‘sunshiners’, referring to the sorts of glinting, shiny beetles which may be seen dashing about on sun-baked paths in the summer months. In attempting to christen all the British ground beetles with English names (a work in progress), I have adopted ‘sunshiners’ for the bulk of the genus Amara, though I have used ‘moonshiners’ for the strongly nocturnal species, of which A. fusca is one. The name ‘Wormwood Moonshiner’ refers to the foodplant of A. fusca.

Making the foodplant connections

The first Breckland specimen was found by torchlight searching and was spotted on the ground surface of a sparsely-vegetated sandy roadside verge. In retrospect, this was a very lucky find: I have seen many dozens of A. fusca since but have never seen another on the ground! Further work by Brian Eversham and myself at the Wangford roadside established that the best way to find the species was by sweep-netting the vegetation at night, with the species being very strongly associated with Mugwort Artemisia vulgaris.

Nocturnal sweeping for carabids and particularly for A. fusca seems to be most effective from about an hour after dusk. As these beetles spend the day concealed in the soil, it is presumed that they need about an hour to have climbed high enough on the plants to be sampled by sweeping. How long sweeping remains effective into the night depends on the weather: as temperatures fall, beetles drop or descend again.

A. fusca is an autumn species with Breckland records spanning the period from 6th September to 13th October probably coinciding with softer, ripening seed. Outside of this period there are only two Breckland records that I’m aware of: 15th May and 14th June.

Having discovered that A. fusca could be found by nocturnal sweeping of Mugwort in the autumn, searches further afield discovered the species at Maidscross Hill, Lakenheath, West Suffolk. Having read in Lindroth’s (1986) work on the carabids of Fenno-Scandia that A. fusca is associated with Field Wormwood Artemisia campestris, a rare speciality of the Breckland, I visited Britain’s largest remaining native population of Artemisia campestris at the Brandon Artemisia Reserve and on 12th September 1993 found 6 specimens. The Brandon Artemisia Reserve has subsequently proved to be probably the best site for the beetle in Britain.

Observations on A. fusca at the three known Breckland sites suggest that Artemisia campestris is the better foodplant, supporting a greater density of the beetles than Artemisia vulgaris. In 1993, the Wangford roadside where A. fusca was found was only about 100 m from a soon-to-disappear population of Artemisia campestris, already then down to one or two plants. Presumably, the population of A. fusca switched from Artemisia campestris to Artemisia vulgaris as its favoured host-plant dwindled to extinction. I think Maidscross Hill may also have been a former site for Artemisia campestris.

Distribution of Artemisia campestris

Artemisia campestris known as the Breckland Mugwort or Field Wormwood is a characteristic species of steppe vegetation in the parts of mainland Europe which experience a continental climate: a zone to which Breckland has many faunal affinities. It was given Endangered (RDB1) status by Perring and Farrell (1983) but I’m not sure what it’s latest status is (please tell me!). Preston et al. (2002) considered it to be restricted to a few sites in the Brecks as a native but with alien occurrences on the Glamorganshire coast of South Wales, and elsewhere in Britain.

Native in Wales

Both Amara fusca and Artemisia campestris have been recorded from Crymlyn Burrows, Glamorganshire. I think for two such rare species to occur at Crymlyn Burrows, they must either both have been introduced there together, or they must both be native there. It is conceivable that beetle and plant could have been introduced together if the plant was introduced with roots and soil from a wild, native population. But that seems pretty unlikely. So I suggest that the Glamorganshire records of Artemisia campestris should be reappraised as native plants.

Additional support for this suggestion comes from the recent discovery of a plant of Artemisia campestris at Crosby sand-dunes in Lancashire. This plant has been ascribed to subpsecies maritima (Dune Wormwood) and it seems as though the South Wales plants are also of similar appearance: relatively prostrate compared to the more erect Breckland specimens.

Things to be done

It would be good to use the experience gained of finding Amara fusca in the Brecks to re-find it at Crymlyn Burrows. A single specimen of A. fusca was recently collected on a Newport development site by Alex Ramsay (confirmed by Brian Eversham) so it would also be worth surveying some of the former Artemisia campestris localities on the coast eastwards from Crymlyn to Newport.

Wherever Amara fusca is found it will be important to ensure that there is a large, dense population of mature, ungrazed Artemisia campestris plants setting abundant seed every year.

Link: There is a page on the Buglife website about Amara fusca.

Comment, 24th March 2010: Andy Jones (CCW Higher Plant Ecologist) writes (via Adrian Fowles):

“We visited the Crymlyn population last year with two researchers (John Twibell and Joan Xirau) who have been studying coastal Artemisia in Europe.  I think it was Charles Hipkin who first suggested that the Crymlyn population resembled A. campestris maritima (reportedly native from Denmark to Iberia) and the idea was supported by Quentin Kay but the matter was never clarified.  However, the Crosby Dunes population revived the issue and John Twibell and Joan Xirau were both strongly of the view that these plants were native (along with raising the subspecies to a full species A. crithmifolia).

In short I think this adds to the gathering evidence and specialist view in favour of a native status – but it would be useful to follow up Dr Xirau’s work, since I think he was going to explore the molecular evidence with the specimens he collected.”

References

Hyman, P.S. (revised Parsons, M.S.) (1992). A review of the scarce and threatened Coleoptera of Great Britain. Part 1. U.K. Nature Conservation: 3. Peterborough: Joint Nature Conservation Committee.

Lindroth, C.H. (1986). The Carabidae (Coleoptera) of Fennoscandia and Denmark. Fauna entomologica Scandinavica, volume 15, part 2. Leiden: E.J. Brill.

Perring, F.H. and Farrell, L. (1983). British Red Data Books: 1. Vascular plants. Second edition. Lincoln: Royal Society for Nature Conservation.

Preston, C.D, Pearman, D.A. & Dines, T. (2002). New atlas of the British and Irish flora. Oxford: Oxford University Press.

Telfer, M. G. and Eversham, B. C. (1994). Amara fusca Dejean (Carabidae) established in Britain. The Coleopterist, 3, 35 – 36.