Guides to British Beetles

7. Brachinus, Omophron, Loricera, Broscus and MiscoderaGround Beetles (Coleoptera; Carabidae)

Omophron limbatum Spangled Button-beetle

Brachinus sclopeta Streaked Bombardier Beetle

Brachinus crepitans The Bombardier Beetle

4.5 - 7.5 mm

5 - 6.5 mm

A very distinctive ground beetle which is unlikely tobe confused with other species. It resembles awater beetle more than a typical ground beetle.The elytra have 15 striae and the scutellum is notvisible as it is hidden under the pronotum.

Inhabits sandy shores of lakes and pools, especiallyrecently worked sand pits. Most often found onareas of very fine silty sand and on quicksand.Mainly nocturnal but may be found during the dayby splashing water over damp sand, the beetles willemerge from the sand and run on the surface.Rare and confined to a few sites in Kent, EastSussex, Norfolk and Suffolk.

Distinguished from Brachinus crepitans bythe red markings on the elytra andcompletely red antennae.

There are old records from Devon, Kent andEssex. It was thought to be extinct inBritain before being rediscovered in Londonin 2005.

Bombardier beetles have a characteristicappearance with a very narrow pronotum and head.They are named after their ability to spray a hot,caustic fluid from the tip of the abdomen indefence. The entire upper surface is covered in veryshort hairs (visible under x10 magnification).

Brachinus crepitans has completely darkelytra and the antennae are darkened. Theadults are very variable in size because thelarvae parasitise the pupae of other groundbeetles including Amara and probablyHarpalus and Ophonus. The size of the adultis determined by the size of the host pupa.

A scarce species found in scattered localitiesin southern England and south Wales. It is mostfrequently found on the coast where it occurs on sea-walls, drier areas of grazing marshes and other openhabitats. Inland colonies occur in open habitats such asquarries and grasslands in chalk and limestone areas.

These genera of ground beetles are distantly related but covered together asthey contain one or two species only. This guide will enable identification ofthe two Brachinus, and single Omophron, Loricera, Broscus and Miscoderaspecies found in Britain.

Omophron limbatum Spangled Button-beetle

Brachinus crepitans The Bombardier Beetle

Brachinus sclopeta Streaked Bombardier Beetle

6 - 10 mm

Adults are veryvariable in size.

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© John Walters 2010 47 Oaklands Park, Buckfastleigh, Devon TQ11 0BPTel (01364) 643916 www.johnwalters.co.uk 1.1 May 2010

pronotum

head

fore-tarsi antenna

jaws

elytron(plural elytra)

peduncle

scutellum

scutellarstria

striae

leg femur(plural femora)

tibia

tarsal segments

tarsus(plural tarsi)

length (mm)Thanks to Mark Telfer for comments, providing the English names and the photo of a Broscus burrow.

Loricera pilicornis Hair-trap Ground Beetle

Superficially similar to other small groundbeetles eg. Agonum but distinguished bythe long bristles on the antennae. Theseare used to trap springtails. Each elytronhas 12 striae (most ground beetles have 9plus the scutellar stria). There are 3 deeppunctures on the 4th elytral interval.

A very common species which flies readilyand is found in a variety of habitats. Loricera pilicornis Hair-trap Ground Beetle

Broscus cephalotes Strand-line Burrower

16 - 23 mm

A very distinctive ground beetle.Matt black above with very faintstriae on elytra. Head nearly aswide as pronotum with large jaws.

A widespread and locally commonspecies found on sandy shores andoccasionally inland in sandy habitatseg. The Brecks in East Anglia.Burrows into sand during the day.Most frequently found underdriftwood along the strandline. It isnocturnal and may be found walkingon the sand after dark.

Broscus cephalotes Strand-line Burrower

Miscodera arctica Moraine Burrower

4.5 - 7.5 mm

Similar in appearance to Broscuscephalotes but much smaller insize. Shiny upperparts with rowsof small pits along striae. Eightpits across the base of theelytra. Legs reddish brown.

A scarce species found on well-drained heather moorland in northWales, northern England andScotland. There is one recordfrom Exmoor, Devon.

Miscodera arctica Moraine Burrower

6 - 8.5 mm

Showing long bristleson the antennae.

Newly-excavatedburrow in sand.

Eight pits across baseof elytra. Scutellum onpeduncle.

femaleall tarsal segmentsthe same width

male*first 3 segmentsof fore-tarsi widerthan 4th and 5th

* except Omophron which hasfirst 2 segments of fore-tarsiwider than 3rd, 4th and 5th.

Elytra showing striae.Scutellar stria highlighted.

Phot

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Mar

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