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 🙂

 

Shield bug egg cases and hatchlings

This two-tone patch of egg cases underneath a cherry leaf caught my eye. On looking closer I saw that the darker patch was a huddle of newly hatched shield bugs alongside their egg cases. Each perfectly spherical little egg case has a perfectly round hatch where the tiny bug has climbed out. And, more curiously, each white egg case has a black marking on it that looks just like somebody has stamped the outline of a moth on it – like nature’s own quality assurance mark 🙂

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Shield bug egg cases and hatchlings

Honeydew : aphid poo

For the last few weeks, the weather here has been very calm, dry and increasingly warm. Conditions are ideal for aphids and their numbers are booming.

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An aphid on juniper – if you look very closely you can see a drop of honeydew coming out of the aphid’s rear
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This juniper has quite a heavy infestation on the undersides of the branches (but the colour variation is natural – it’s a variegated type).

Sometimes I hear people say that particular trees (especially lime trees) or shrubs create honeydew. And people don’t like that, especially if it drips down onto cars, or if it grows mould and mars ornamental plants. However, it isn’t really (not directly) the trees or shrubs that make honeydew. Honeydew is aphid poo (it can come through a few other bugs too). The aphids pierce through into the vascular system of the plant and the plant’s sap more or less flows out through the aphid – in at one end, a little bit is digested by the aphid, and a slightly thicker stickier ‘honeydew’ continually seeps out of the other end…

Return of the maybugs

I know that maybugs (Melolontha melolontha) are considered “pests”, but I was very happy to spot a pair in that garden yesterday. They were cuddled up together, wrapped in the leaves of a hazel tree, just like they were having a duvet day. As the wind whipped the branches of the tree around, the bugs stayed snug in their little shelter of leaves, munching away.

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Maybugs cuddling up together in a tent of hazel leaves

Today I went back to see if I could spot them again, but I could only find one of them. The lifecycle of these chafers is impressive: they will have been in the earth for two or three years as grubs and then they will have changed to their adult form last autumn and waited the winter out underground. So, it’s slightly conceivable that this pair might just be related to the pair I spotted three years ago

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The now solitary maybug, still munching its way through hazel leaves.

 

Queen wasp – nest building

When I opened my shed door yesterday morning, I almost walked straight into this queen wasp who had just started building a nest inside the door frame.

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A queen wasp just beginning the foundation for her nest

This queen will have over-wintered and is now desperate to build a nest, lay her eggs (that were fertilised at the end of last summer) and start rearing her young. Sadly for her, the doorway of a shed I use every day wasn’t a good choice.

I felt bad about it, but I removed the nest stem that she’d started to build, and then left the shed wide open all day to discourage her from coming back. I watched for a while as she frantically searched for where she’d begun building. But by the end of the day, she wasn’t around, so hopefully she found a more suitable place to nest.

Through most of the year, wasps catch small insects and caterpillars to feed to their young, and in doing that, they can be very helpful as garden pest controllers. So I don’t mind wasps living in the garden, but just not right in the doorway of one of the sheds!

Cherry slug worms

When I noticed, a few days ago, that some leaves on a young cherry were being grazed, I didn’t give it much thought. It’s the time of year when caterpillars are everywhere and leaves are naturally heading into decline.

A cherry slug worm grazing on a cherry leaf
A cherry slug worm grazing on a cherry leaf

But, later on, a slimey black splodge on one of the cherry leaves made me look a little closer. And there was my first cherry slug worm. I’d learnt about cherry slug worms being a pest almost all over the world, but I had never seen one in the flesh, so to speak.

Cherry slug worms are the larvae of a sawfly – Caliroa cerasi. They coat themselves in shiney bluish-black gloop to put birds off from eating them. This gloop works so well that the slug-worms confidently feed in broad daylight on the upper surfaces of leaves. There they eat away all the flesh, just leaving a skeleton of leaf veins.

From this angle you can almost see through the black gloop to the greeny-brown larva within
From this angle you can almost see through the black gloop to the greeny-brown larva within

Cherry slug worms are also supposed to be quite happy eating hawthorn leaves, so after these two had had their photos taken, I moved them to a hawthorn bush. If they’re unlucky, they’ll be parasitised by a wasp; if I’m unlucky, they’ll pupate in the litter under the bush and emerge as flies to lay eggs and make more slug-worms next year!

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Extrafloral nectaries. Pardon?

Lots of plants have glands that secrete nectar, the sweet liquid so attractive to bees and other insects. However, these glands aren’t always in the flower. When they’re outside the flower, they’re called extrafloral nectaries.

Ants feeding from the extrafloral nectaries (the red bumps at the leaf base) on a young cherry tree.
Ants feeding from the extrafloral nectaries (the red bumps at the leaf base) on a young cherry tree.

The function of these extrafloral nectaries has been conjectured for years and years, but still no one is really certain what their role is. Back when Charles Darwin was writing On the Origin of Species he noted that:

Certain plants excrete sweet juice, apparently for the sake of eliminating something injurious from the sap. … This juice though small in quantity is greedily sought by insects; but their visits do not in any way benefit the plant.

This remains one of the hypotheses for the role of the extrafloral nectaries – that they are helping with them elimination of undesirable compounds.

The other hypothesis, which is more popular these days, is that the extrafloral nectaries attract beneficial insects which help in defending the plant from “pests”.

I have to say, in my experience the glands attract mainly ants who, as Darwin noted, feed greedily from them. Meanwhile the aphids still come and begin feeding on the plant leaves. Then the ants, which are there in abundance having been dining at the extrafloral restaurants, set up their aphid farms, defending the aphids from would be predators like ladybirds. The ants then live a particularly happy life, lounging drunkenly around the extrafloral nectaries and milking their aphids.

New growth on a young cherry heavily infested with black aphids which are being farmed by ants
New growth on a young cherry which is heavily infested with black aphids (causing characteristic leaf curl) which are being farmed by ants

There must be more to this than meets the eye though, otherwise it would be a bit of a suicidal strategy.