Scarlet Caterpillarclub, Cordyceps militaris

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Scarlet Caterpillarclub, Cordyceps militaris

Scarlet Caterpillarclub, Cordyceps militaris.

As a fan of both insects and fungi, I was thrilled to see my very first Scarlet Caterpillarclub fungus, Cordyceps militaris, on a trip to the Norfolk Brecks last Sunday.

I had wanted to see this species for some time and to find not just a single Cordyceps militaris but eleven of them in a single location, in short grass around an oak tree on a grassy heath, was absolutely stunning. The fungus is an infrequent find in the British Isles, and seems to be commoner in the north and west (note 1).

Scarlet Caterpillarclub is a parasitic fungus that grows on the larvae and pupae of moths. The unfortunate host is a caterpillar that has buried into the soil to pupate but is instead consumed by the fungus, which sends up a bright orange club through the turf to spread its spores. When viewed with a hand lens, the bottom of the club (the stipe) is smooth but the upper surface of the club looks bobbly. Cordyceps militaris is an ascomycete fungus and the bobbles are perithecia, small flask-shaped fruiting bodies which contain spores (note 2) .

If you gently extract a Scarlet Caterpillarclub from the soil it is possible to find its unfortunate host. We did this with one of the fungi we found; ours was still a caterpillar but the Lorn Natural History Group website has superb photographs of the fungus growing from both pupae and caterpillars (note 3). The fungus normally grows from the head end of its host.

Cordyceps militaris is the commonest of about a dozen Cordyceps species that have been recorded in the British Isles (note 4) and there are around 400 species worldwide. Cordyceps comes from two Latin words: cord, a club, and ceps, head. Militaris is also from Latin and may refer to the way this fungus attacks, overpowers and occupies its host.

Following DNA sequencing, some species of Cordyceps have now been moved to the genera Ophiocordyceps and Tolypocladium. Several species are so-called “zombie fungi” because of the way they take over an insect’s body and alter its behaviour.

Probably the most (in)famous example is Ophiocordyceps unilateralis, a parasite of carpenter ants, found in tropical forests. The fungus influences the ant’s behaviour, making it travel outside the nest to a more humid place suited to the fungus, removing its instinctive fear of heights and making it climb the stem of a plant, where it clamps its jaws around a leaf vein and waits to die. Fungal hyphae grow out of the ant’s feet to attach it more firmly to the plant and then the fungus digests the ant from within and sends a fruiting body out through the base of the ant’s head, to spread its spores. Some of these spores will infect another ant, to continue the lifecycle. Throughout the process, the fungus is absent from the ant’s brain and the fungus’ influence on the ant appears to be a chemical one, possibly through ergot alkaloids (chemically related to LSD) (note 5).

Ophiocordyceps sinensis, the Chinese Caterpillar Fungus, has a similar lifecycle to our Scarlet Caterpillarclub but is found in Tibet, Bhutan, Nepal, India and China and mainly infects the caterpillars of Thitarodes ghost moths (note 6).

These caterpillars spend their time under the ground, where they feed on roots. They can become infected with fungus spores through their mouth or skin as they move down through the soil. Once infected, a caterpillar moves slowly into a position ideal for spore dispersal (just the right depth for the fungus to push its club above the surface) and its skin changes colour from brown to milky white. Fungal hyphae fill the caterpillar’s body cavity and it is long dead by spring when the fungus sends a stalk up above ground and produces spores to infect the next generation of caterpillars.

The Chinese Caterpillar Fungus has been known about and used in Chinese medicine for generations (note 7). It has been used to treat an assortment of conditions including fatigue, respiratory and kidney diseases and cardiac dysfunction. Research is now being carried out to assess these medicinal properties (note 8).

Ophiocordyceps sinensis suddenly became a lot more popular in 1993 after two unknown female athletes, Wang Junxia and Qu Yunxia, broke records races in China’s National Games in Beijing and their trainer revealed that they had taken Ophiocordyceps sinensis supplements. 

The popularity of Chinese Caterpillar Fungus has had a major impact on the regions where it grows. On the plus side, it has provided much needed income and employment (for whole families) in mountainous areas. But as early as 2005, the New Scientist was reporting “Chinese fungus fad poses eco-threat“. By then the harvest from the Tibetan Plateau and Himalaya Region was around 140,000 kg per annum, with 2,000kg poached from Bhutan alone in 2002, and prices had reached some $7,000 a kilogram, half that of gold. By August 2012, the price had soared to $110,000 per kg in Beijing, almost three times the current price of gold.

Ophiocordyceps sinensis is only found in alpine meadows at altitudes of about 3000–5200 metres (note 9) and its range is retreating upwards as global warming takes hold. Harvesters scour the meadows and use a small pickaxe to remove a patch of grass, together with roots and topsoil, to reveal the fungus emerging from its host. The entire fungus and its attached caterpillar are removed intact, cleaned and sold to itinerant caterpillar fungus traders.

The annual collecting season lasts from about mid-May to mid-July. In this time, collectors can dig up whole meadows, cut alpine shrubs for fuel and dump rubbish, including human faeces which can contaminate water sources. The influx of thousands of people can disturb livestock and wildlife (including the rare Snow Leopard). There have also been some violent disputes over harvesting areas.

Not surprisingly, yields of Ophiocordyceps sinensis appear to be falling (note 10) and the sober conclusion to this tale of overexploitation is: “It now appears increasingly possible that caterpillar fungus, if not properly managed, may be a one-time ecological windfall rather than the inexhaustible resource it once appeared to be.”

Meanwhile, our very own Cordyceps militaris is being investigated too (see Das et. al 2010, for example). Like Ophiocordyceps sinensis, taking extracts of the fungus appears to improve tolerance to high intensity exercise and it may have uses in treating some cancers.

Large-scale artificial cultivation of Ophiocordyceps sinensis in its host is not possible, though small scale production is now taking place. But cultures of Cordyceps / Ophiocordyceps fungi grown without the fungal host – anamorphs (the asexual form of the fungus), grown in liquid cultures or in grain – allow suppliers to produce Cordyceps extracts and powders. The Real Mushrooms website explains more.

It is also possible to grow the sexual stage of Cordyceps militaris in bulk (minus caterpillar). Mushroom Revival, based in Austin in Texas, grow it on a vegan substrate and sell it as a dried fungus or as a tincture. A quick search online gives lots of results for various Cordyceps extracts for sale in the UK too. The Real Mushrooms website says that extracts of this form of the fungus contains the active ingredient cordycepin (3?-deoxyadenosine) in much higher amounts than Cordyceps sinensis.

Some websites say that Scarlet Caterpillarclub isn’t edible but Alan from Minnesota, a chef, offers a recipe on his Forager Chef website: Cordyceps with Linguine, Shallots, Watercress and Chives. He says the ones he bought from San Francisco “weren’t mind blowing, but they definitely weren’t bad“. He wonders whether the fungus tastes the same without its caterpillar – it’s a question of “terroir“.

I don’t plan to try Cordyceps any time soon, but for fans, the RealMushrooms website has links to recipes containing Cordyceps powder, including Sexy Mushroom Truffles and Muscle Recovery Bone Broth.

Cordyceps and Ophiocordyceps fungi have even inspired a video game, The Last of Us, which is set in a post-apocalyptic United States (note 11). In a world of Covid-19 and Trump, that seems a bit too real for comfort, so I’ll stick to going outdoors in the healthy air to look for more fascinating fungi.

Notes

Note 1 – A couple of years ago Norfolk Fungus Study Group found Scarlet Caterpillarclub in the grassland at Felbrigg Hall in North Norfolk, on one of their field trips (which I missed). At time of writing the NBN Atlas doesn’t include this record.

Note 2 – Some club fungi, such as Pipe Club (Typhula fistulosa), are Basidiomycetes.  In contrast to the Scarlet Caterpillarclub, their clubs have a smooth surface.

Note 3 – A variety of species are parasitised but the Lorn Natural History Group website says “The caterpillars are usually well decomposed and hard to identify with certainty”. This was certainly true of our specimen.

Note 4 – (So far) I have only seen the Scarlet Caterpillarclub.

Cordyceps ophioglossoides, the Snaketongue Truffleclub, Cordyceps capitata, the Drunmstick Truffleclub and Cordiceps longisegmentis, are three more British species, but instead of insects they parasitise another fungus, the False Truffle, Elaphomyces granulatus. Their clubs grow from the False Truffle’s underground tubers.

Note 5 – I recommend the book “Entangled Life – How Fungi Make Our Worlds, Change Our Minds and Shape Our Futures” by Merlin Sheldrake, The Bodley Head, London (2020) – Ophiocordyceps unilateralis is discussed in Chapter 4, “Mycelial Minds”.

Jennifer Lu’s National Geographic article “How a parasitic fungus turns ants into ‘zombies'” (April 2019) and its accompanying video are worth a read and watch.

See also “Fungi That Infect Insects: Altering Host Behavior and Beyond” by Shang et.al. (2015).

However, rather than kill their host, some Ophiocordyceps fungi actually help several Japanese species of Cicada to take up nutrients from their diet of plant sap, which is high in sugars, but low in other essential nutrients. See “How To Tame A Zombie Fungus” (Yong, 2018).

Note 6 – A review of Ophiocordyceps sinensis by Wang and Yao in 2011 found 56 potential insect hosts, primarily “ghost moth” larvae of the genus Thitarodes (37 species).

Note 7 – Although its use may go back some 2000 years, the first written references come from a fifteenth-century Tibetan medical text. The first mention in a Chinese medical text is in 1757.

A Chinese name for Ophiocordyceps sinensis is Dong chong xia cao. Like the Tibetan name yartsa gunbu, it means ‘winter worm, summer grass’. The fungus was once thought to transform from an animal to a plant during summer and back to an animal for the winter.

Note 8 – See, for example, Choda 2017 and Belwal 2019 and the RealMushrooms.com website.

Note 9 – Its habitat ecology (including soil types and associated plants) has been studied in Nepal by Sigdel et. al (2017).

Note 10 – For example, official yields in Nepal went from 3.1 kg in 2002 to 2442.4 kg in 2009, before dropping precipitously to just 1170.8 kg in 2011.

Note 11 – Kyle Hill wrote about the game and Cordyceps in the Scientific American blog in 2013: see “The Fungus that Reduced Humanity to The Last of Us“.

Common Toadflax, Linaria vulgaris

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Common Toadflax, Linaria vulgaris

Earlier in the month I wrote about Devil’s-bit Scabious, Succisa pratensis. Another British wild flower that gives a splash of late colour is Common Toadflax, Linaria vulgaris. Here in Norfolk, its yellow flowers light up grassy road verges, it also flowers along grassy rides in Breckland and I grow it in our garden.

Linaria vulgaris is a hardy perennial with stems up to 90cm (36 inches) tall, with narrow, linear bluish-green leaves all round the stem, topped with lovely yellow two-lipped flowers, like a Snapdragon (Antirrhinum majus) but with a long spur at the back. The flowers have a darker yellow or even yellow-orange centre, where the lips meet. (See the Wildflower Finder website for lots of lovely photos.) Common Toadflax can come into flower as early as June and its flowers can usually be found into late October.

Common Toadflax is widely distributed and common in England, Wales and lowland Scotland, but scarcer in Ireland. It grows in open grassy places, on stony and waste ground, in hedge banks, on road verges and railway embankments and on cultivated land, especially on calcareous soils. It is a native of temperate areas of Europe and Asia as far as China, including the British Isles (note 1).

It has been introduced into Japan, North America (Canada and United States), Australia, Chile and South Africa. The CABI Invasive Species Compendium lists countries and states where the plant is found, along with the dates and impacts of introduction (note 2). Where introduced, Linaria vulgaris can be an agricultural weed, especially in Alberta in Canada. It can also compete with native vegetation, as in parts of the United States, including Yellowstone National Park. On the plus side, its roots can help to stabilise soil.

Common Toadflax has creeping roots bearing adventitious buds and over time plants can form dense mats. They can also reproduce by seed (note 3).

Like Ribwort Plantain, Weasel’s-Snout and Sharp-leaved Fluellen, Linaria vulgaris is a member of the Plantaginaceae (the Plantain family) (note 4).

Linaria means “resembling Linum“, because the foliage of some species looks a bit similar to flax (Linum). Vulgaris means “common”. Other English names include Yellow Toadflax and Butter-and-eggs (both from the colour of the flowers).

Common Toadflax makes an ornamental and drought-tolerant garden plant, though its growth habit means you may need to keep an eye on its spread. I grew my plants from seed (from Emorsgate Seeds). Up until recently I grew them in large containers, but I have now planted some in a sunny bed in the front garden. In the past I tried to introduce container grown plants on the allotment but without success. I don’t know why they didn’t thrive – they should like sandy loam.

Linaria vulgaris has a long history of herbal use, listed on the Plants for a Future website. The plant was used as a laxative and diuretic. Extracts were used internally to treat oedema, jaundice, liver diseases, gall bladder complaints and skin problems and externally for haemorrhoids, skin eruptions, sores and malignant ulcers. However, it should only be prescribed by a qualified practitioner and should not be given to pregnant women. A yellow dye is obtained from the plant and a tea made from the plant has been used as an insecticide.

The Wild Flower Finder website lists several of the compounds found in Common Toadflax, including the lignan glycoside liriodendrin and two pyrroloquinazoline alkaloids, peganine and vasicinone.

The “toad” in the English name “Toadflax” may also relate to a medical usage. Apparently  the plants were used to treat bubonic plague and a false link may have been drawn between the words “bubo” (an inflammation of the lymph nodes) and “Bufo“ (a toad).

Common Toadflax flowers have nectar in their flower spurs and this attracts bumblebees. In Britain, only longer-tongued species such as Bombus hortorum (Garden Bumblebee) and Bombus pascuorum (Common Carder Bee) are able to get to this through the flower tube, but shorter-tongued species can overcome the problem by cutting a hole in the side of the spur and robbing the nectar without pollinating the flower.

I usually only see Common Carder Bees on the flowers but other species of bees will visit – the Emorsgate Seeds website features a Wool Carder Bee (Anthidium manicatum) hovering by a Common Toadflax plant (note 5).

Quite a few insects feed on Common Toadflax and the CABI website lists several, though it is mainly interested in them as biological control agents. One species I would like to find is the Toadflax Leaf Beetle, Chrysolina sanguinolenta. It is a rare and local insect but it occurs in Norfolk, especially in the Brecks, so if I keep on searching I may see it one day.

Notes

Note 1 – The BSBI Online Plant Atlas considers it to be a British native but the Wild Flower Finder website says that Common Toadflax may have been introduced to the UK as a garden plant. This is certainly true of its relative, Purple Toadflax, Linaria purpurea, which is native to Italy.

Clive Stace lists eight species of Linaria, plus three hybrids, in his “New Flora of the British Isles“ (Fourth Edition, 2019). Only Linaria vulgaris is native; Linaria repens (Pale Toadflax) is an archaeophyte (an alien which became established before AD 1500) and the others are neophytes (aliens which became established after AD 1500).  (Strictly, the cut off date is 1492, when Christopher Columbus voyaged to the New World.)

There are about 150 species of Linaria worldwide.

Note 2 – Information in this paragraph comes from https://www.cabi.org/isc/datasheet/30828#toDistributionMaps. CABI is the Centre for Agriculture and Bioscience International. Read more about the organisation and its work on its website: https://www.cabi.org.

Note 3 – The CABI fact sheet states that the roots are “widely but wrongly referred to as rhizomes (underground shoot structures)”. Plants “can establish from root fragments as short as 1cm long and the root system may penetrate up to one metre deep and several metres laterally, but shoots mainly originate from the shallower roots at depths of 2 – 5 cm”. Seed production and germination rates are usually low. Up to 100 seeds may form per capsule but viability may be no more than 25%.

Note 4 – Stace treats Linaria, Antirrhinum, Misopates, Veronica (Speedwells), Digitalis (Foxglove) and several other genera as the family Veronicaceae (Speedwell family).

Note 5 – We get Wool Carder Bees on Purple Toadflax (Linaria purpurea) in our garden.

Devil’s-bit Scabious, Succisa pratensis

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Devil's-bit Scabious, Succisa pratensis

Devil’s-bit Scabious, Succisa pratensis, at Buxton Heath, late August 2020.

We are now at summer’s end. Days are noticeably shorter and there are fewer flowers and insects, but there are still many things to look at and enjoy. Not least are late flowering plants such as Ivy (and its attendant insects), Grass of Parnassus and Devil’s-bit Scabious.

Devil’s-bit Scabious, Succisa pratensis, is flowering at the moment in Norfolk, and attracting plenty of hoverflies, butterflies and bees.

It is a perennial plant which has a basal rosette of leaves. From July onwards the plants send up nodding stems up to one metre (40 inches) tall, topped with flower heads, a tight bunch of buds (described as like boxing gloves) which open out into lilac-blue pincushions.

Succisa pratensis in bud

Succisa pratensis in bud: “like boxing gloves“.

Succisa pratensis

Succisa pratensis – open flower, like a pincushion.
Many more photos can be found on the Wildflower Finder website.

Devil’s-bit Scabious is one of three native species of scabious in the British Isles, the others being Small Scabious, Scabiosa columbaria, and Field Scabious, Knautia arvensis. Along with Teazels (Dipsacus sp.), these plants form a natural grouping: family Dipsacaceae (the Teasel family), or subfamily Dipsacoideae, part of the Caprifoliaceae (Honeysuckle family) (note 1).

Small Scabious grows in dry, calcareous grassland and in rocky places such as cliff tops, and Field Scabious grows in dry, grassy places on light soils. In contrast, Devil’s-bit Scabious is found in a wide variety of grassy places, including woodland rides, heathland and grassland and in mires, and in the uplands on cliff ledges and in ravines.

In Norfolk, Devil’s-bit Scabious grows in very different places: in valley mires and fens such as at Upton Fen and Buxton Heath, but also on the dry chalk ramparts of an Iron Age fort at Warham Camp. These areas have one thing in common:  more dominant species of plant are being held in check either because the soil is not particularly fertile, or because of grazing pressure.

Succisa pratensis is found throughout the British Isles in suitable areas where the grassland has not been “improved” (note 2), but it has had a widespread decline in southern and eastern England since 1950.

Scabious plants were used to treat skin conditions such as scabies (a contagious skin infestation caused by the mite Sarcoptes scabiei, note 3), and even bubonic plague. Devil’s-bit Scabious is still used in the treatment of eczema and other skin conditions. Other medicinal uses listed on the Plants for a Future website include the treatment of coughs, fevers and internal inflammations, and externally to treat bruises or conjunctivitis. Young shoots are edible and sometimes used in spring salads.

It is illegal to dig up plants without the landowner’s permission (note 4) and I don’t recommend it for Devil’s-bit Scabious, but if you did you would find that the root is black and rather short. The suggested reason was that the Devil bit the bottom of the root off, because he was angry at the plant’s medicinal qualities.

As well as being a great source of nectar for insects, Devil’s-bit Scabious is the foodplant of the Marsh Fritillary, Euphydryas aurinia. The butterfly is mainly found in the western half of Britain, having suffered a dramatic decline since the 1970s. I first saw one in The Burren in Ireland in 1985, with my next sightings over thirty years later, near Oban in Scotland (2018) and in the Lake District (2019), where the butterfly has been reintroduced.

Marsh Fritillary

Marsh Fritillary, Euphydryas aurinia.

We grow Small Scabious and Field Scabious in our garden. The former is in a gravel garden (now much wilder than when I wrote about it in 2013) and the latter in our wildflower meadow. Both do well in my dry, sandy loam. I haven’t tried growing Devil’s-bit Scabious but it would make a lovely addition to a garden, is very hardy and will flower for a long period.

The RHS website says that Succisa pratensis will grow in any moist soil in sun or partial shade and is excellent for peaty bog garden. Given that it grows wild in well drained conditions at Warham Camp, it might be worth experimenting if your soil is drier. Pot-grown plants are available online (for example, from Claire Austin and Sarah Raven), or you can buy seed (Emorsgate Seeds). Seed is best sown in the autumn: I might even give it a try.

Notes

Note 1 – Clive Stace considers the Dipsaceae to be a family, in his “New Flora of the British Isles“. (Fourth Edition, 2019.)

Note 2 – See Note 3 in my post about Green-winged Orchids.

‘pratensis‘ means ‘growing in meadows‘.

Note 3 – In Latin, scabere means to scratch.

The subspecies of mite Sarcoptes scabiei canis can infest dogs, cats, foxes, pigs, horses and sheep, causing sarcoptic mange.

The condition is very unpleasant in foxes and will lead to the death of an infected fox if it is not treated. It is probably the reason why fox numbers in our part of Norwich have crashed in recent years. (We no longer have foxes next door.)

The National Fox Welfare Society offers free mange treatment.

Note 4 – The Wildlife and Countryside Act (1981) makes it illegal “to uproot any wild plant without permission from the landowner or occupier” in Britain. See the Plantlife website for more information.