Section J
Most of the beetles here are from (unless otherwise stated) the group Cantharidae, known as the Soldier beetles. I've listed a few of the more common ones and a brief pictorial guide (with the aid of Cantharid queen Steph Skipp) to the often less-covered smaller species.
She would love it if you can send her any records via iRecord
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There are many similar species and for the larger, brightly coloured species there are some excellent free guides already available.
If you like pictures try Mark Gurneys picture guide
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If you like something a bit less colourful then Kieth Alexander & Martin Harveys field guide is HERE
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For a key to all of the UK's species, there's also The Fitton Key
Cantharis decepiens
A very common species found throughout Britain in a range of habitats
ID Features
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7.5-8.5 mm
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sandy tan colour
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Pronotum tan with dark 'Phallus' shaped marking
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black head
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Shiny tan elytra completely covering wings covered in short hairs
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Rhagonycha fulva
Often occur in large numbers towards the end of the summer, known as 'blood sucker' or 'bonking beetles'.
Despite frequently being seen 'bonking' they have never been documented sucking blood and instead feed on pollen and smaller insects.
ID Features
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8- 10 mm
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sandy tanelytra with black tips
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red and black legs
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red head
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S. French
Cantharis rustica
Probably the most frequently encountered large species of soldier beetle in the UK
ID Features
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9.0 - 13.0 mm
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Black wing cases
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Black legs with red (femora) bases
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Red pronotum with central heart-shaped dark mark
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Malthodes/ Malthinus
Small (under 5mm) black and yellow soldier beetles, often beaten from deciduous trees but occasionally turn up in moth traps.
They usually have black elytra with distinctive yellow tips They can be a bit of a pain to separate, but if you can separate the 2 Genera, you are already halfway there.
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It is possible to split the 4 Malthinus species fairly simply (see below guide) however Malthodes are another kettle of fish and may require genitalia dissection.
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For a key to all of the UK s soldier beetles, including genitalia diagrams
Malthodes flaveolus
Splitting the Two
Malthinus sp.
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More boggle 'eyed'
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roughly triangular head
mandibles with a tooth
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Bell shaped pronotum
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Head and/or pronotum more course with rough punctures
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Pale legs
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Malthodes sp.
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Less boggle-eyed in comparison (although some males do buck this trend)
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rounder head
mandibles without a tooth
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A more square-shaped pronotum
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Head and/or pronotum smooth, at most finely punctured
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Darker legs
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Malthinus- 4 species
Cantharid whizz, Steph Skipp showed me the easiest way, by far, to split the 4 British species was through pronotum patterns.
Be aware that often these markings can merge (in the case M. flaveolus particularly) and can be pretty variable, but its a great way to begin to split them, when used in conjunction with other ID characteristics
M. seriepunctatus​
Pronotum patterns in UK Malthinus species
M. flaveolus ​
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M. balteatus
M. frontalis
ID Features
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Punctures in rows
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Pronotum with Black' hourglass marking
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Scutellum with at least apex yellow
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ID Features
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random punctures
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Pronotum with 2 lines, may merge to form a 'V' shape
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ID Features
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Pronotum with thick vertical band with parallel sides
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Scutellum entirely 'dingy brown' (fuscous)
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Elytra have a horizontal(transverse) white line across it
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ID Features
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Entirely black pronotum ​
M. seriepunctatus​
M. flaveolus ​
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M. balteatus
M. frontalis
Malthodes- 12 species
Of the 12 Uk species, I feel only one ID easilly recognisable in the field IF it is a typical example.
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Personally I would recommend keying any other suspect Malthodes out properly.
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Be aware there are completely dark forms that do occur and that they can be incredibly variable.
Malthodes marginatus
ID Features (of a typical specimen)
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Pronotum with a lateral border when viewed dorsally (left)
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Pronotum with all 4 corners paler​, often forming a 'blurred' cross shape
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Male with bulbous eyes and abnormally long antennae
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Male (Left) & Female (Right) Malthodes marginalis)
The odd ones out
These beetles are not soldier beetles, (Cantharidae) and simply superfiscially resemble them, for ease of identification I have put them here.
Malachius bipustulatus
S.French
ID Features
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approx 5.5-6.0 mm
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metallic green body and legs
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2 pink, well defined spots on elytra ends
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Transverse pronotum (Wider than long)
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Second antennomere strongly serrate
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April-August
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Only likely to be confused with the smaller Cordylepherus viridis which has smaller spots on the elytral ends, is overall smaller (4.0-5.5mm), quadrate pronotum (as long as wide) and with a less serrated second antennomere.
The Malachite beetle, incredibly common throughout the spring and summer months
image via: Wikicommons