By John Meiklejohn, John Partridge and Harry Green
The Bombardier Beetle Brachinus crepitans (Linnaeus, 1758). Photo Roger Key
The most surprising find during tetrading described above was a site containing Bombardier Beetles. John Meiklejohn found them amongst a small sample of insects taken home for identification.
The RECORDER data-base describes the species as follows:
Bombardier beetle Brachinus crepitans (L 1758) Coleoptera: Carabidae. A 6-10 mms long, black and red beetle living under stones and leaf rosettes in short dry grassland, usually on chalk or limestone. A mainly southern species. Famous for its crepitating defence.
The species is listed as Nationally scarce (B).
Luff (1998), in the Provisional Carabid Atlas, states that it occurs across southern England and into South Wales with most modern records from coastal areas, and although there are many old inland records, the more recent ones are confined to the Cotswolds and Northamptonshire limestones, and the boulder clays of Huntingdonshire. He says that typical habitats are calcareous grasslands, chalk quarries and arable field margins. The map, adapted from the Atlas, shows the distribution. Note the only dot in Worcestershire (and in the 100 km square SO) is marking SO84 and probably represents the only known previous Worcestershire record, which is from the Brotheridge Green old railway line wildlife reserve, near Malvern. This record, from the early 1970s, was made by Ian L Crombie, and we have no further details. The beetle presumably lived on the old railway track ballast: the reserve was much more open and stony at that time than it is today. We do not know if the beetle is still there.
The new record from 26th June 2001 near Honeybourne is also associated with an old railway site which is very open and stony. It is possible that Bombardier Beetles may occur on similar sites elsewhere - an old railway line beetle!
The species is found throughout central and southern Europe and North Africa. There are many other species worldwide and the biology of American species has been worked out.
Bombardier beetle Brachinus crepitans: British distribution. Solid dots post 1970, circles pre 1970. From Luff 1998.
The Bombardier Beetle Brachinus crepitans is 6-10 mms long, of typical ground beetle shape with a rather narrow thorax. The head and thorax are red and the abdomen greenish black. A lens reveals a general hairiness. They are famous for their crepitating defence. When alarmed they eject explosive pulsating jets of noxious gas from their rear end which can be directed against an attacker (such as an ant or another beetle), appearing as puffs of smoke with a popping noise. Early naturalists thought it resembled gunfire! The spray is released from the anus and directed by the mobile tip of the abdomen at the predator. It contains hot p-benzoquinone produced explosively from components held in paired glands. Each is double, comprising a muscular compressible inner chamber containing a reservoir of hydroquinones and hydrogen peroxide, and a thick walled outer chamber containing oxidative enzymes. When threatened the beetle contracts the reservoir forcing the contents through a valve into the reaction chamber. Here an exothermic reaction produces p-benzonquinone at 100C. The jet of gas is a series of rapid pulses. (paraphrased from Gullan & Cranston 1994).
Not much is know about the breeding biology of Brachinus crepitans, The larvae are apparently ectoparasitic on the pupae of other beetles and the species seems to be associated with Amara convexiuscula (a ground beetle) and Ocypus ater (a staphylinid beetle) on the south coast (Luff pers com).
Thanks to Roger Key, Martin Luff and Mark Telfer who responded to Harry Green's emails seeking more information on the species. Roger Key kindly provided the photograph.
|GULLAN PJ & CRANSTON PS. 1994. The Insects: An outline of Entomology. London: Chapman and Hall.|
|LINDROTH CH. reprint 1992, original German language edition 1944. Ground beetles of Fennoscandia. Part 1 Specific knowledge regarding the species. Pages 265-267. Andover: Intercept (the reprint).|
|LINDROTH CH. 1974 reprint 1996. Coleoptera, Carabidae. Handbooks for the Identification of British Insects, Vol 4, Part 2. London: Royal Entomological Society.|
|LUFF ML. 1998 Provisional Atlas of Ground Beetles (Coleoptera, Carabidae) of Britain. Huntingdon: Biological Records Centre.|
There are several web sites offering information. Many creationists' web sites use this species as an example of a species which could not have evolved but must have been created because of its remarkable explosive chemistry!
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