Tag Archives: Cinnabar Moth

Natural History

Plague of Ragwort in Richmond Park

Ragwort by the thousand … and as yet hardly any Cinnabar Moth caterpillars. But I’m getting ahead of myself.

Ragwort is not just a common weed, but a curious one. It used to be a Notifiable Weed to the Ministry of Agriculture and Fisheries (more Ag. than Fish., probably). This was because it gave livestock that incautiously ate it, fresh or in hay, a violent stomach upset and sometimes caused death. So, farmers were obliged to report it and destroy it.

Why so dangerous? It contains Cardiac Glycosides, yup, chemicals that interfere with heart rhythms. Presumably natural selection has favoured this as animals end up not eating too much of the plant, which favours its survival. That includes cows and most insects.

However, a few beasties can tolerate the poison; and the Cinnabar Moth is one such. Actually, it goes a step further — it benefits from the stuff. Its caterpillars are large, conspicuous, and slow-moving; they’re also striped brilliant orange and black, warning coloration. That says “eat me, you’ll regret it”, and it’s an honest signal; any bird that tries it will indeed be violently sick, at least, and won’t try eating larvae that look like that again. Ever.

However however, one bird can tolerate the poisonous caterpillars: the Cuckoo. It arrives and feasts on the conspicuous and presumably delicious, nutritious larvae which nobody else will touch with a bargepole and rubber gloves.

Even more however, there’s a catch. The caterpillars are Very Hungry (this is a literary reference). They munch through the Ragwort like there’s no tomorrow, until it’s all gone. Then they pupate, turn into beautiful cinnabar-red and grey adults, lay eggs, and die. The Ragwort is already dead, obviously. And Cuckoos and everyone else who comes alone the next year won’t find a Ragwort plant or a Cinnabar moth for love nor money.

Then, gradually, a few surviving seeds grow into Ragwort plants. There are no Cinnabar caterpillars to do the damage on them. They go forth and multiply, as the bible has it. After a year or two there are Ragwort to the Left, Ragwort to the Right, and Ragwort all around. The man at the Min. of Ag. and Fish (or whatever it’s now called) spends all day answering phone calls about Ragwort (only he doesn’t, he’s got fed up of doing it by now). The few Cinnabar caterpillars have food in plenty and they breed like rabbits. Well, like Cinnabar moths. And the cycle goes round again.

So there you have it. Plague of Ragwort? Don’t tell the Ministry, but do wonder at the power of Nature.

Ringlet Butterfly

P.S. It was a lovely day for butterflies, too, with Small Coppers nectaring on Ragwort flowers; Ringlets by the Pen Ponds; Small Heaths knocking seven bells out of each other; and (Cabbage) Whites and Red Admirals about too. Grasshoppers skipped about; a Lizard ran across a path into the grass. A big flock of Canada Geese, with a few Greylags, grazed peacefully. Ants rebuilt their flooded-out nests.

Natural History

Handsome Bugs! June in Wraysbury

Male Banded Demoiselle, on Reed
Cinnabar Moth, with hardly any Ragwort to eat, on Alfalfa
Reed Stem Borer on Buttercup. This family of Sawflies (no waist) is long and thin; the larvae tunnel in the stems of various plants, this species being one of the longest and living in, you guessed it, Reed stems.
Male Common Blue Damselfly, with a little “wine-cup” atop each abdominal segment

As well as these elegant and colourful insects, there were Red Admirals and Meadow Browns flying today, but overall very few butterflies.

Natural History

Ichneumon Attacks Cinnabar Caterpillar; Small & Essex Skippers

Ichneumon Wasp and Cinnabar larva, just after the 'sting'
Ichneumon Wasp and Cinnabar larva, just after the ‘sting’

Well, what a piece of luck. I was just inspecting the ragwort where the Cinnabar caterpillars were clustered (by the rail of the Anthill Meadow), and had seen they had grown, and had dispersed from one stalk to three or four — when I saw an Ichneumon approach with the usual dancing flight. Grabbing the camera, I took three photographs, of which the above is the last, and I think the prettiest.

Ichneumon Wasp pointing ovipositor at Cinnabar larva
Ichneumon Wasp pointing ovipositor at Cinnabar larva

This is the second photo: the wasp has her abdomen curled beneath her body, towards her prey (ok, host, she’s a parasitoid).

Ichneumon attacking Cinnabar larva
Ichneumon attacking Cinnabar larva

And this is actually the first photo, the wasp very close to the caterpillar, her ovipositor sharply folded under her thorax: the caterpillar has just twitched sharply, presumably on being ‘stung’ with an egg now fatally implanted in its body. The cinnabar is aposematic, full of bitter and poisonous chemicals, which don’t protect it against this sort of attack, evidently.

Down by the pond there were plenty of Azure damselflies, one Common Bluetail, and some really tiny newly-metamorphosed froglings hopping about in the mud. A Small Skipper perched obligingly on a Yellow Iris leaf, not far from a plump Iris Sawfly larva.

Small Skipper on Yellow Iris leaf
Small Skipper on Yellow Iris leaf

Down at the Picnic Meadow, ignoring a picnic and dropped bicycle in the entirely dry brown grass, an Essex Skipper visited some Bramble flowers. It’s just like the Small Skipper, but without the orange on the antennae.  A Meadow Brown sat in the grass.

Essex Skipper on Bramble flower picnic meadow
Essex Skipper on Bramble flower picnic meadow

In the woods, a Holly Blue flew high, near a Holly tree. A Small White completed the butterfly tally for the walk.

Natural History

Spanish Summer … in Chiswick

Azure Damselfly Wheel
Azure Damselfly Wheel

The pond is really low in the heat (and the grass is brown and crisp, and Birch trees large and small are dying). There are Large Red, Azure and Bluetail damselflies urgently laying eggs; this pair of Azures was in the incredibly complicated mating posture that we call the Heart or Wheel, with secondary genitalia locked on in preparation for transfer of the spermatophore; then the female does her thing with sperm storage. Bizarre.

Red Admiral - battered but still flying
Red Admiral – battered but still flying

If there’s an insect equivalent of a World War II Hurricane landing safely with most of its tailplane, rudder, and wings shot away, this battered but defiant Red Admiral must be it. I saw the odd outline and thought “Comma?” – then I saw the colours and thought “Hot weather, beaten-up butterfly, Painted Lady”; then it landed and I realized what it was.

Heat. It’s apparently the hottest day in England for nine years: right now it’s 33ºC here, and remarkably sticky.

Cinnabar Moth Caterpillars on Ragwort
Cinnabar Moth Caterpillars on Ragwort

Among the dry grass are an increasing number of Ragwort plants; at the moment, having seen just one Cinnabar moth flying briefly, there is also just one plant covered in Cinnabar caterpillars. They are aposematic: brightly coloured black and orange, warning, like wasps and bees, of their poisonous cocktail of chemicals picked up from their food plant. They seem to grow in numbers until they devastate the Ragwort population, which then crashes … which wipes out the Cinnabar moth, until a new outbreak of Ragwort restarts the cycle. It seems to me the nearest thing to the Lotka-Volterra model ever, given that the model basically predicts wild swings in population of “predator” and “prey”. For lynx and snowshoe hares it’s a wildly wrong model; for moths and Ragwort, maybe there’s something in it.

Making croc coffins (plant boxes) for the car park
Making croc coffins (plant boxes) for the car park

We spent some happy hours cutting up a lot of wood to make two large “planters” to disguise the green metal box of a shed in the car park. The plants will need constant watering, which sounds a bit of a problem, but maybe for annuals it’ll do fine. We nicknamed the planters “crocodile coffins” as they are the size of young crocs and perfect for their funerals, if crocs need ceremonies.

Yesterday evening we had a fine view of the conjunction of Venus and Jupiter in the western sky, Venus an elegant bright crescent (evening star) on our side of the sun, Jupiter a smaller and dimmer star, visibly a complete disk, far away from us of course on the other side of the sun. The 80mm birdwatching telescope did a good job; of course it would be lovely to have a big astronomical telescope to get a bigger view.

Natural History

This Week’s Insects at Gunnersbury Triangle

Comma butterfly
Comma butterfly

Comma, Red Admiral, Small White, Meadow Brown, Holly Blue, Speckled Wood butterflies this week. A Cinnabar Moth, the first of the year, flew over the bank near a patch of Ragwort, the food plant of its caterpillars. Let’s hope she laid some eggs.

Tree Bumblebee Bombus hypnorum
Tree Bumblebee Bombus hypnorum

Macrophya Sawflies mating on Hogweed
Macrophya Sawflies mating on Hogweed

Bluetail Damselfly on Iris
Bluetail Damselfly on Iris

The first Bluetail Damselfly appeared today; Azure and Large Red Damselflies still about.

Honey Bee on Bramble flower
Honey Bee on Bramble flower

Conservation, Love of Nature, Natural History, Natural Patterns, Nature Reserves

Of Hoverflies and Bush Crickets

Large hoverfly in dark woodland space
Large hoverfly in dark woodland space

An English Summer is, as the saying goes, three fine days and a thunderstorm. Or, going out with sunhat, suncream, sunglasses… and a pullover and raincoat, just in case. Today it started out cold with a chill north-north-easterly wind, but quietened down and became rather too hot to work comfortably.

A tree had fallen across the glade in the Gunnersbury Triangle where the beekeeper is going to station one of her hives. I soon threw off my pullover, and my rainproof jacket never left my rucksack. The soft willow wood was no trouble to saw up, and I dragged the branches to the dead-hedge without much effort. A lot of small holm oak, an invasive alien species from the Mediterranean (think Ligurian coast) has sprung up from old stumps, so they joined the pile.  A Blackcap sang to me while I worked.

The butterfly transect revealed very little, though some Commas are encouragingly laying eggs. As for other insects, several species of hoverfly, from tiny and slender to large wasp mimics and a fine one largely black, perhaps a bee mimic, were active. They hover, perch and sunbathe, or dash and chase each other (specially the large black ones) aggressively. I had fun trying to photograph one actually in the air, you can see the atmospheric but not very useful result above. It does give something of an idea how much they whiz and dash about, hovering always on the qui vive.

Ragwort is getting more and more abundant on the reserve; today, Helen spotted some tiny (probably first instar) Cinnabar Moth caterpillars on one of the plants; an adult visited me while I worked.

The Peacock Butterfly caterpillars of last week seem all to have pupated in hiding somewhere; there are quite a few younger ones still on the stinging nettles, so there will be at least two lots of adults.

Knot Grass caterpillar on bramble
Knot Grass caterpillar on bramble

We found a Knot Grass moth caterpillar (a Noctuid moth) on a bramble. It is hairy and aposematic, with brown hair but without the four long brown ‘shaving brush’ tufts of the Vapourer moth caterpillar (a Lymantriid or Tussock moth), which we’ve also found here.

But perhaps the insect I was happiest to see was this young Bush Cricket, resting on a flower for no particular reason, and taking a risk as its fine spotted green camouflage was totally compromised by its white and yellow flowery background. It must be the first one I’ve seen this year.

Young Bush Cricket
Young Bush Cricket

I have always loved natural patterns. The bark of this Aspen tree looks almost as if it encodes symbols in some cuneiform notation.

Natural Pattern: Aspen bark, almost seeming like a form of writing
Natural Pattern: Aspen bark, almost seeming like a form of writing

Conservation, Natural History, Nature Reserves

Summer Bugs at Gunnersbury Triangle

Cinnabar Moth on rusty False Oat Grass
Cinnabar Moth on rusty False Oat Grass

Ragwort is at full height now and will soon be flowering. A few adult Cinnabar Moths are about; they will mate and lay eggs on the ragwort, which is in several places around the reserve, and then we will have the fine black-and-orange banded caterpillars in quantities, eating the Ragwort to pieces. They are poisonous with alkaloids taken up from the plant, so few predators eat them: an exception is the Cuckoo, which seems able to cope with the chemistry.

Iris Sawfly on Yellow Iris, with examples of how it damages leaves
Iris Sawfly on Yellow Iris, with examples of how it damages leaves

Iris sawfly caterpillars are starting to chew inroads into the spearblades of the Yellow Iris; they are rather like moth caterpillars, but with rows of little dots on their backs and different numbers of prolegs.

Fox run down grassy bank
Fox run down grassy bank

It looks as if there are young foxes about; a very well-worn run goes straight up the grassy bank into the bushes, and the grass nearby is much trodden down.

Neighbours
Neighbours

The new buildings towering over the reserve are approaching their final shape; it will be a relief when the roar of heavy engines and the squeal and clatter of caterpillar-tracked bulldozers subside into history. There was a horrible accident on the building site this week when something fell from a crane; three workers were injured, one seriously, and the air ambulance arrived, followed by the health and safety inspectors.

 

Conservation, Natural History, Nature Reserves

Flaming June

Large Red Damselfly
Large Red Damselfly

After all the rainy weather  (I even found a large toadstool – in June: The Blusher, Amanita rubescens), today was suddenly hot, at least it seemed so while digging brambles out of the ramp meadow, raking up the scythed Cow Parsley in the full sun, pitchforking it into a barrow and carting it off to a deadhedge. It was a satisfying conservation job, one of those where you can see what you have done, and it looks a lot better after than before. The area is supposed to be a meadow; we successfully suppressed the overgrowth of brambles two years ago, leading to a burst of rather nice Garlic Mustard and its attendant Orange Tip butterflies last year: and a second wave of Cow Parsley that must have seeded itself really well, because it suddenly covered the area this year. Now that it’s all cut, we may hope that grasses and smaller herbs may get going: some Ground Elder at least has begun the process.

In the pond and on the vegetation for a way around it, including atop the hump, Large Red Damselflies are soaking up the sunshine, and flying in cop, egglaying – the females dip the rear half of their very long abdomens in the water to reach an aquatic plant such as Myriophyllum on which they place the eggs.

The butterfly transect was again quiet, but graced by the first Cinnabar Moth of the year: there is a fair bit of Ragwort coming up, and this adult must be newly hatched out of a pupa, presumably at ground level or below as the plants are annual.

Sure enough, after I had finished the transect, the first Holly Blue butterfly of the year, beautifully fresh and new, skipped its bright quick flight just in front of the hut.