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Lampyridae – Glow-worms

The Glow-worm Lampyris noctiluca must be one of Britain’s most widely known and best loved beetles, up there with 7-spot Ladybird and Stag Beetle. If you are prepared to invest 10 minutes of your time, watch this beautiful and informative film about British Glow-worms. I’ve seen larvae and adult females much more frequently than I’ve seen adult males. Though bioluminescing females are the show-stealers, males are well worth seeing, if only to marvel at their extraordinary eyes – there’s almost nothing of the head except for two enormous eyes! The male’s head is completely hidden under the pronotum in dorsal view.

Male Glow-worm Lampyris noctiluca

Larval Lampyris noctiluca are very similar to adult females but smaller, with softer pronotum, blunter hind-angles to the pronotum and pinkish spots at the hind-angles of the body segments. Identification of larvae and adult females is dealt with in more detail here.

There are two other, much rarer, species of lampyrid on the British list:

Phosphaenus hemipterus Until recently, this species was known mostly from a scatter of single records from built-up areas or on disturbed ground, consistent with a non-native species that is occasionally introduced but does not become established. However, in 2007 an established population was discovered by John Horne (2007) on his nature reserve at Bursledon, Hampshire (see this article for more info), and in 2009 a new site was found near Tunbridge Wells (Kent/ Sussex) (mentioned here).

Lamprohiza splendidula. Known in Britain only from two male specimens taken in Kent during 1884 by an unknown collector, one of which is labelled “Leeds, Kent, Aug. 84 [= 1884] beaten from hedge” (Alexander, 1988; Allen, 1989). Both specimens are in the Glasgow Museum collections.

I have been muddling through for a while without much confidence that I’d recognise either of the rarer species if I was lucky enough to find them, as adults, let alone as larvae. Could they be overlooked as just Lampyris noctiluca? Identification of all three species as adults and larvae is well covered by Raphaël de Cock at this webpage with illustrations and hyperlinks to photos (many no longer working!).

Identification of adult Lampyridae in Britain.

Lampyris noctiluca
Larger species, length (from the front of the head to the apex of the abdomen) 9.5 to 19 mm. Antennae about equal in length to length of pronotum. Male: elytra covering the whole of the abdomen and joined along the suture; hind wings fully developed. Female: wingless and larviform; blackish-brown above.
Alexander (2006) notes that both sexes can bioluminesce from the apex of the abdomen, though the males are slightly less bright.

Phosphaenus hemipterus
Smaller species, length (from the front of the head to the apex of the abdomen) 5 to 7.5 mm. Antennae about twice the length of the pronotum. Male: elytra shorter than the abdomen (about 1½ times the length of the pronotum) and clearly separate; hind wings absent. Female: wingless and larviform; blackish-brown above.
Joy (1932) notes that both sexes can bioluminesce from the apex of the abdomen. De Cock states that females glow from a ventral pair of light organs in the penultimate segment but only when disturbed.
See this photo of an adult male.
See this photo of a larva.

Lamprohiza splendidula
Medium-sized species, length of males 8 10 mm, females 10 mm. Antennae about equal in length to length of pronotum. Male: similar to L. noctiluca but with two large transparent windows on the pronotum above the eyes (these absent or indistinct on Lampyris noctiluca); pronotum much more transverse and with rounded hind-angles (distinct, acute hind-angles in Lampyris noctiluca). Female with visible wing rudiments; ivory coloured.
Females bioluminesce from several points visible from both above and below the abdomen. Males are ‘fireflies’, glowing brightly in flight. Take a look at this excellent set of photos.

I don’t know whether I am guilty of outrageous optimism … probably Lamprohiza splendidula will never be seen again in Britain. But time and again ‘extinct beetles’ (and moths!) have come back from the dead – it’s amazing how some species can evade detection for several decades before showing up again. The danger is that we all assume it is extinct and don’t keep an eye out for it, and then there’s little chance of it being rediscovered.

Keith Alexander would be glad to receive records of glow-worms for the national Cantharoidea & Buprestoidea Recording Scheme: details here.

References

Alexander, K. (1988). Cantharoidea and Buprestoidea Recording Scheme Newsletter no. 2. May 1988.

Cooter, J. and Alexander, K. (2006). Lampyridae. P. 70 in Cooter, J. and Barclay, M. (eds) A coleopterist’s handbook. 4th edition. Orpington: The Amateur Entomologists’ Society.

Alexander, K.N.A. (2003). Provisional atlas of the Cantharoidea and Buprestoidea (Coleoptera) of Britain and Ireland. Huntingdon: Biological Records Centre.

Allen, A.A. (1989). Lamprohiza splendidula (L.) (Col., Lamyridae) taken in Kent in 1884. Entomologist’s monthly magazine, 125: 182.

Horne, J. (2007). Lesser Glow-worm, Phosphaenus hemipterus (Goeze) (Lampyridae) in Hampshire. The Coleopterist, 16, 110.

Joy, N.H. (1932). A practical handbook of British beetles. 2 volumes. H.F. & G. Witherby.


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