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Cantharidae – Soldier Beetles

Cantharis decipiens © Alan Outen

Soldier beetles are apparently so-called because of their boldly-patterned colouration in reds, blacks, yellows and oranges, recalling the military uniforms of history. They are summer beetles, adults emerging from the pupal state in late April, May or June and dying off between June and September depending on the species. They are a familiar sight to anyone inspecting the flowers of Hogweed and other umbellifers, or generally sweeping or beating in grassland, scrub or woodland.

It is a small family of 41 species in 7 genera. The family can be divided into two. The majority of the family are medium to large, boldly coloured species in the subfamilies Cantharinae (4 genera, 24 species) and Silinae (1 species) which I think of as the true ‘soldier’ beetles. And then there are the 16 small species in Malthinus and Malthodes forming the subfamily Malthininae which are generally blackish with or without yellow markings and rarely noticed until they are on the beating tray or in the sweep-net. All are soft, flimsy and weakly chitinised beetles, especially the Malthinus and Malthodes. All the species are good fliers except for the recently discovered flightless Malthodes lobatus and whatever this species from Stodmarsh is.

Malthinus flaveolus: most of the malthinines have these bright yellow tips to the elytra.

They can be identified using
Mike Fitton’s excellent keys (from his PhD thesis), which Brian Eversham has updated. Brian has mentioned the two major changes to the British list since the keys were written:

(i)     that Malthodes brevicollis has been deleted from the British list, and
(ii)    that Malthodes lobatus has been discovered here.

There are a couple of name changes too:

(i)    Ancistronycha abdominalis is keyed out as a Cantharis but is now separated out into genus Ancistronycha;
(ii)   Cantharis bicolor is now called Cantharis cryptica.

Be warned that some of the Cantharis species in particular are exceptionally variable in colour pattern though others are highly constant. Fitton’s keys make allowance for all known variants but if you want to get to the stage where you can identify cantharids in the field, you need to be confident you know the range of variation in each species.

Keith Alexander’s Field Key to Soldier Beetles (Cantharinae and Silinae) has been in circulation since 1986. Recently, Martin Harvey has produced a revamped version which Keith has kindly allowed us to put online: download the new Field Key to Soldier Beetles (391KB PDF) here. Keith advises “this doesn’t cope with all the variation but should help people to get to grips with the species”. For those familiar with Keith’s original, Martin’s 2011 version has laid out the table in a clearer format, made some small adjustments to the wording for clarity, and added a second page summarising the habitats and status of each species (based largely on Keith’s atlas).

Be warned also that keying out female Malthodes with Fitton’s keys is probably never going to be 100% reliable. Fortunately, Malthodes are particularly easy to sex in the field, the males having much more bulging eyes and longer antennae (i.e. better developed sensory organs for tracking down females) so just pick out males for identification.

Male (top) and female (bottom) Malthodes flavoguttatus.

The other indispensable literature on the family is Keith Alexander’s (2003) Provisional atlas of the Cantharoidea and Buprestoidea (Coleoptera) of Britain and Ireland, published by the Biological Records Centre. Order from their website. It covers four smaller families too: Buprestidae (jewel beetles), Drilidae (one species: Drilus flavescens), Lycidae (net-winged beetles) and Lampyridae (glow-worms). The Lycidae, Drilus and two of the three British Lampyridae are also covered by Fitton’s keys.

Keith continues to run the Cantharoidea and Buprestoidea Recording Scheme (see here for details) and is willing to identify or check difficult specimens: he has been a great help to me by identifying specimens and offering advice. Note that the ‘Cantharoidea’ superfamily is not used in the most recent British checklist but refers to the families Cantharidae, Drilidae, Lycidae and Lampyridae, all now incorporated into the Elateroidea.

Finally, and most importantly, NEVER POOT A CANTHARID!!! They will kill and chew up every other invertebrate in your pooter, typically starting with your most exciting captures and leaving some of the dross specimens unharmed. (Do I sound bitter??). So if you are going to collect one, tube it individually or give it a sniff of ethyl acetate straight away.

Though I’ve never reared one, I frequently see what I believe to be cantharid larvae by grubbing at the soil surface. They are quite dark and have a velvety coating of hairs. There is a good paper on cantharid larvae, including a key to genera, by Mike Fitton (1975).

A presumed cantharid larva.

Thanks to Keith Alexander for commenting on a draft of this web page.

Reference

Fitton, M. (1975). The larvae of the British genera of Cantharidae (Coleoptera). J. Ent., 44: 243 – 254.


4 Comments

  1. Jim Jobe says:

    Many thanks Mark!

  2. Bryan Sage says:

    As always, very helpful and instructive and much appreciated. The only problem I have is that I cannot seem to acess Keith Alexander’s A.4 Field Key !!

  3. markgtelfer says:

    Thanks Bryan, My mistake – I have now made the Field Key publicly accessible. Should be OK now.

  4. Greg says:

    For those who can live without a hard copy, Keith’s atlas is available as a download from the NERC Open Research Archive http://nora.nerc.ac.uk/

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