Species of the Month - October 2017

Scarlet Caterpillar Club

Cordyceps militaris

Cordyceps militaris   Cordyceps militaris

Scarlet Caterpillar Clubs can be found anywhere that caterpillars occur; in woodland, grassland and most other kinds of habitat.  Sometimes there is just one club, sometimes a few together.  They are similar in shape to fungi such as Wrinkled Club (Clavulina rugosa) or Smoky Spindles (Clavaria fumosa), but are unrelated. as those are basidiomycetes and this is an ascomycete.  Its surface is rough with perithecia tips which release the spores.  Basidiomycete club fungi have a smooth surface.  There are other Cordyceps species but they do not have this colour and shape.  If it looks like C militaris then you can be confident that it is.

Cordyceps militaris

Above: fruitbodies growing in grazed turf, Lismore

Right: fruitbody growing on fallen branch

  Cordyceps militaris

When the spores are released only the lucky few that land on a butterfly or moth caterpillar will survive.  When the caterpillar enters the soil or leaf litter to pupate, the fungal mycelium begins to grow inside it, replacing the caterpillar's own insides.  Sometimes this happens before the caterpillar has pupated, and then when you dig the fungus out you find its base attached to a dead caterpillar.  The right-hand one above was growing on some rotten wood so it was quite easy to dig out.  The result is shown below.

Cordyceps militaris

This is what we found when we dug out the fungus from the dead wood.  The fungus is growing from a dead caterpillar, which we thought might be that of the Emperor Moth.  The caterpillars are usually well decomposed and hard to identify with certainty.

At other times, the caterpillar pupates first, and the fungus is found growing from a pupa (making the host species even harder to identify).

Cordyceps militaris

This one from our 2015 Sea Life Centre bioblitz had three fruitbodies growing from one pupa.

Cordyceps militaris

Caterpillar Clubs are not common anywhere but they seem to like short vegetation in thin soil over rock, especially limestone rock.  Something has been grazing on these ones.

Cordyceps militaris

Photo by Jan Hamilton of Scarlet Caterpillar Club on moss-covered rock outcrop in grassland, on our Kentallen cycle track field trip in Oct 2014

Please send in your Scarlet Caterpillar Club sightings using the form below, or email sightings@lnhg.org.uk with the details if you prefer.  If you are not sure of the identity of your fungus, please send a photo to sightings@lnhg.org.uk, or put one on the LNHG Facebook page.

Date of sighting 
Grid reference 
Name of finder 
Your name (if different) 
Email (not needed if I already know it!) 
Any other details, e.g numbers, habitat    


By filling in this form you agree that the information contained in this form may be collated and disseminated manually or electronically for environmental decision-making, education, research and other public benefit uses in accordance with the LNHG data access policy.  Your email address will not form part of the record and will not be passed on to anyone.

Carl Farmer
LNHG Biological Records Manager

Note you can still send in records for past species of the month.  Here are the previous October species:

Oct 2016 - Blackening Waxcap
Oct 2014 - Crimson Waxcap
Oct 2013 - Ballerina Waxcap
Oct 2012 - Dryad's Saddle
Oct 2011 - Small Tortoiseshell

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This project is supported by Scottish Natural Heritage

All photos and other content copyright Carl Farmer except where stated.  The 3rd, 7th and 8th photos are Jan Hamilton, and the 6th is Sallie Jack.  Mouse over photos to see credits.