Metamorphosis

At the end of last summer, the caterpillars of the large white butterfly (Pieris brassicae or cabbage white) left their food plants in the garden and went marching en masse. Most of them marched right out of the garden: they climbed sheds, walls and fences, seemingly knowing where they were heading. But one of them choose to stop and pupate in a stone outhouse where I keep ladders and various bits and bobs.

Throughout the winter, I’ve been careful not to knock the chrysalis off. And for the last few weeks I’ve been watching for “it” to happen: for the butterfly to emerge. Today was the day.

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This was the pupa on 12th May: it was starting to change colour and plump up
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This was first thing this morning (19th May). The wings are clearly visible, squished up against the side and the whole thing looked fit to burst – which it was!
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Here it is, freshly emerged – the empty case that the butterfly crawled out from is towards the bottom, just left of centre

I know it is “just” a cabbage white, and something of a pest, but I am awestruck by the complexities of nature and very happy that this one survived the winter 🙂

 

Solitary bees – swimming and pollinating

Last week I spotted this little solitary bee struggling in the pond. I helped it to a rock at the edge and watched as it dried itself off and eventually flew away.

Solitary bee drying out after falling in the pond
Solitary bee drying out after falling in the pond
...a little bit drier
…a little bit drier

Meanwhile the apples are coming into flower and I’ve been keeping an eye out for bees visiting them. However, there seem to be very few bees around so far this year. The few carder and bumblebees that are here seem to be ignoring the apple blossoms and focusing on the bugle (Ajuga reptans) and rosemary flowers instead.

Carder bee on bugle flowers
Carder bee on bugle flowers

However, there is one little solitary bee busily working its way through the apple flowers – it was there yesterday and again today. Or maybe there are lots of them, but I’m only seeing one at a time: either way, I’m glad that somebody is helping to make sure there will be an apple crop later this year.

Solitary bee on apple blossom
Solitary bee on apple blossom

(I think these solitary bees are Tawny Mining Bees – Andrena fulva – but I’m not at all sure: we’re lucky to have lots of different species of burrowing bees locally, but I don’t know enough to be able to identify them.)

Peacock butterfly caterpillar

Peacock butterfly caterpillar
Peacock butterfly caterpillar – this one has wandered away from the defoliated nettle it was living on. Its orange feet (prolegs) mean it is quite “grown up”, for a peacock caterpillar.

The shiny, spikey black caterpillars of peacock butterflies feed on nettles.

We’ve fallen out of love with nettles – probably because they sting! – but they used to be more widely valued: as a vegetable, a medicinal herb and for making a (rather nice) textile. They’re a good plant for recycling nutrients and are rich in nitrogen, making them a valuable addition to the compost heap. And, of course, they’re good for wildlife.

Perennial nettles do spread easily, but they’re also easily pulled up, especially if you mulch around them. So, if you have the space, they’re a worthwhile addition to any wildlife garden area.

Thunderworms are go!

Thunderworms (Mermis spp) are pale, thread-like worms, up to about 12cm long, that seem to appear from nowhere after heavy downpours in the spring and early summer.

thunderworm (Mermis spp)

Yesterday morning, after two days of persistent rain and warm temperatures, this thunderworm was draped across the flowers of a thyme bush.

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Thunderworms are parasites, but not of humans – they’re completely harmless to us and pets*: they parasitise insects.

For most of their lives these thread-like worms live underground, but they need to surface to lay their eggs. They can only do that during very damp conditions so that they don’t dry out – hence they’re only found after rain (or irrigation). The adult female worm climbs as high as it can to lay its eggs on plant material in the hope that the eggs will be eaten by an insect munching on the vegetation. The eggs will then begin their development within that insect, before migrating into the soil to spend a couple of years growing to maturity there.

The name thunderworm came about because the deluges that the worms need to emerge are often accompanied by thunderstorms. Once upon a time it was thought that the worms actually came down from the sky with the rain or the lightning.

*The roundworms that infest dogs and cats (Toxocara spp.) are from a completely different family of worms and are potentially very harmful to humans and pets.

 

Sleeping butterflies

A sleeping comma butterfly
A butterfly sleeping away the winter

I stumbled upon this sleeping butterfly while cleaning out an old pigsty.  It looks quite the worse for wear – covered in dust and slightly caught up in old spider webs – but hopefully, having made it this far through the winter months, it will survive and soon fly away.

Several species of UK butterflies try to survive the winter in their adult form. Of those, the most common are the comma, the peacock, the small tortoiseshell and the brimstone.

To learn more about how butterflies overwinter have a look at this page from the Butterfly Conservation website.

 

Frog spawn

The frogs are spawning. Year after year, they return to precisely the same spot and over the course of a week or so, the clumps of frog spawn pile up one on top of the other.

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A growing mound of frog spawn, 16th Feb 2014.

Last year the frogs here spawned early – at the end of January. Sadly we then had hard frosts throughout almost the whole of March and it ended up being a poor year for the frogs. This year, they’re three weeks later spawning and hopefully they’ll fare better.

It usually takes around four months for the frog spawn to become little froglets here. So these should be “ready” around midsummer.

Even if you don’t have a pond or room for a pond in your garden you can encourage frogs to visit by providing damp places, log piles and piles of stone. If you do provide a water feature for wildlife, no matter how small, it will be appreciated.

Collecting frogspawn to populate your own pond is now discouraged because of concerns about spreading disease and introducing strangers into existing territories. Instead, you are encouraged to provide the right environment and then be patient: given time, the frogs should arrive.

Frogs eat all kinds of flies, grubs and slugs and are an asset to any garden so they’re worth encouraging. And they’re cute.

There’s lots of information about all things froggy, including advice for making your garden frog friendly, at Froglife.

Feeding garden birds: in sickness and in health?

I first heard of Trichomonosis (or Trichomoniasis, as it is sometimes called) as a disease of garden birds about three or four years ago. The media were working with the British Trust for Ornithology and the RSPB to raise awareness of the illness and to encourage reporting of cases of sick birds so that the development of the disease could be better monitored.

Last year, I had first hand experience* of the disease affecting a greenfinch and a chaffinch in my garden: most probably because I was putting food out regularly for the one legged robin. But maybe not… that’s the thing with real life: there’s no “control” like there is in an experiment, so you can never know what might have happened had circumstances been different.

Anyway, in the early summer I saw a sick greenfinch in the garden. I was sufficiently aware of Trichomonosis to wonder whether that was what ailed this bird: its feathers were all puffed up; it was dopey and didn’t fly very far at all; it kept wiping its beak; and it generally looked a bit off-colour and sick.

A sick greenfinch, probably infected with Trichomonas gallinae
A sick greenfinch, probably infected with Trichomonas gallinae

I knew that the advice if you have an infected bird is to immediately stop feeding birds in your garden. And my first thought was to obediently obey this advice, but then I thought a bit more logically about it.

I live in a village and most of the households here feed the birds to some extent. So, if I stopped feeding the birds in my garden, they’d just move to somebody else’s garden…that could mean more mixing of birds, more close contact between them as they scrabbled for less food in a smaller area, and, consequently, the possibility of hastening the spread of the disease. Mmm, that didn’t sound like a clever plan after all. So I decided to continue putting out bird food.

There isn’t a whole lot of data on the prognosis for wild birds infected with Trichomonosis. The illness is caused by a parasite called Trichomonas gallinae. Infestation with this microbe can result in cankers growing in the oesophagus and crop (neck pouch) of birds. These cankers can get so big that they make eating and drinking difficult and the birds can starve to death, or become so weakened they’re susceptible to other ailments or just so lethargic that they’re easy prey, especially for domestic cats. However, often infection with the Trichomonas parasite either has no visible symptoms, or just very mild symptoms that the bird recovers from (and possibly develops immunity to the illness as a result).

There is, however, a lot of information available on the internet about the disease in general, its symptoms and how it spreads. An important point is that it needs to be transferred via a moist medium – it’s not robust and soon dies if it dries out. Consequently, drinking water put out for the birds could be a key place for the spread of the parasite.

So, I also thought about stopping putting water out for the birds. But there are gutters, puddles, troughs and ponds everywhere, as well as all the other gardens that have water bowls and baths for the birds. I was already in the habit of ensuring that the water for the birds was fresh each day and also that the water bowls were frequently cleaned with a bleach solution. So, I decided to continue with providing water too…

There isn’t really a tidy end to this story. I don’t know what happened to the two sick birds that were in my garden. Maybe they died, maybe they got better, maybe a cat ate them: who knows. But I am confident that suddenly stopping providing food and water to birds is going to cause them to go elsewhere, it’s not going to be a cure for the problem. Not unless a whole village or town stops at the same time, which is unlikely. So, if you do feed garden birds just do it as hygienically as you can: there’s nothing more you can do really.

RSPB advice on garden bird diseases including Trichomonosis

BTO information on Trichomonosis

This chapter from a field guide published by the US National Wildlife Health Center has detailed and useful information.

* it’s an assumption based on symptoms that the illness of these birds was Trichomonosis: to know conclusively would require laboratory testing.