Tuesday, 30 August 2011

Mixed bag

These are the last photographs from my usual stretch of hedgerow for several months. The day after I took these, the hedge was cut down to the ground to a distance of a metre from the road on each side for 200 metres. So there won't be anything worth posting from there until next spring. I don't know why the hedgecutter chose this totally inappropriate (and illegal!) time to do the cutting ("it's only weeds and bugs"), but we have to live with these decisions. Unfortunately, the wildlife can't.

Last year I showed a photograph of the capsid bug Lygus rugulipennis. This is its nymph from exactly the same area:
Nymph of  the capsid bug Lygus rugulipennis
If you follow the link back to the original picture, notice how different the adult is from the nymph. This is typical in bugs, and makes identification of nymphs that bit more difficult, since it's normally the adults that are shown.

Udea lutealis is one of the larger micromoths, and is to be seen on practically every verge and hedgerow at the moment. The faint pattern diminishes as the moth gets older, and mature specimens (i.e. a few days old) appear to be a uniform cream in colour:

The micromoth Udea lutealis

I spotted this larva of the Sawfly Arge gracilicornis on Bramble. I had hoped to follow its progress for a few days, but that is no longer possible:
Larva of the Sawfly Arge gracilicornis
I should also mention at this point that I will be unable to continue my 5 year study of the sawfly Nematus pavidus this year, since the Willows were also threshed to ground level and won't have leaves until next year. I hope I can find some more specimens elsewhere.

The fungal rust Puccinia graminis infects many different grasses. This infection is on a stem of False Oat grass:

Fungal rust Puccinia graminis on False Oat grass
I haven't seen very many specimens of the wasp-mimicking hoverfly Sericomyia silentis this year. This one was on Male Fern on the other side of a deep ditch:

Hoverfly Sericomyia silentis

Earwigs are universally despised and, I think, a bit unfairly. They are quite unusual in that they tend to stay in family groups, whereas most other insects abandon their eggs/larvae. This is a male (the pincers are curved) Forficula auricularia:

The earwig Forficula auricularia
This one was photographed in my garden: I found it when checking a pot full of Fuchsia cuttings. Notice how small the wing covers (the squarish area next to the middle leg) are. Earwigs can actually fly, but I rather suspect that they are reluctant to do so because the wings have to be folded around 40 times to get them into such a tiny space.

New identification.

Friday, 26 August 2011

An identification

My last post showed images from a woodland ride which is bounded on the northern side by a mature Spruce plantation, and on the southern side by Beech. Over the last couple of days I have been closely examining some more of the photographs, and I realised that I have a very illustrative set of images of one species of hoverfly that was causing me more than a little bit of bother to identify.

This is the first shot:

My initial reaction was "Cheilosia illustrata, but a very bright specimen". So I rattled off a few more shots as it wandered over the flowerhead:

When I examined the photographs back at the computer, I quickly realised that my initial identification was wrong. Firstly, the face is yellow, and there are no grooves running down between the eyes and face:

Those features rule out Cheilosia.

So what is it?

A quick examination of the wing veins ruled out Eristalis sp., because the Eristalis 'bulge' is not present:

Archive image of the distinctive Eristalis 'bulge' 
Here is the actual wing:

The arrow shows another distinguishing feature of the wing, where the marginal vein curves back to make an obtuse angle with the central vein. This obtuse angle rules out Volucella species. Just to confirm, I checked the aristae, which are the small projections on the antennae. The ones on this specimen are simple and not feathered, so that again rules out Volucella species:

Let's look at the legs:

The legs are clearly not all black, so that rules out Merodon species.

I was struggling at this point, because I had ruled out all of the common bumblebee mimics, and the image didn't match any others in the standard reference book.

I decided to bite the bullet and key the specimen from scratch, which led me to tribe Syrphini, and only one member of that tribe remotely resembles a bumblebee, and that is Eriozona syrphoides. A quick check of the species description for Eriozona syrphoides reveals:

"At first sight, Eriozona is like an outsized Cheilosia illustrata, but the face is yellow in Eriozona."

"Most records are for Spruce plantations or deciduous woodland where spruce is present."

"May to October, with a second peak in August".

Things are looking good for Eriozona syrphoides. But it's a rare species, which I had only seen once before, in another Spruce plantation some 30 km. away. I was still a little bothered that the illustrations didn't match, so I did a quick google search of images for Eriozona syrphoides, and it was immediately obvious that there are two distinct colour forms: one that is in the book and matches my first specimen and another, much brighter version, which is the version I found on Wednesday.

So there we have it:

The hoverfly Eriozona syrphoides (male)
Time taken for the identification? Around two hours.

Eriozona syrphoides is a European species new to Ireland (the first sighting was in 1998) and follows on from sightings in England and Wales in the 1960's. It is closely associated with Spruce plantations (the larvae are predators of aphids that feed on conifers), so the species is clearly spreading as Spruce plantations mature. I'm usually very critical of the negative effect that Spruce plantations have on local biodiversity, but in this case I have to make an exception: Eriozona syrphoides is a very handsome hoverfly.

(Late note: I wonder if the two colour forms are male and female, since my previous specimen was a female). More checking.....

Later note: Once I had finalised this identification, I realised that a specimen shown previously from this same location was actually this species. I have amended the previous page accordingly.

Tuesday, 23 August 2011

What's that yellow thing in the sky?

Sun! We had almost four hours of continuous sun today, so I made a bee-line for the Angelica.

I took around 200 shots of whatever looked good, and these are the highlights:

The Peacock is a butterfly that I see quite rarely. I'm not sure if there were a few of them on this woodland ride today, or if the same one was flying along overtaking me from time to time. The Peacock is a nettle feeder and the late summer generation is emerging now. These will overwinter as adults, emerging in spring as soon as it's warm enough:

Peacock butterfly

Sicus ferrugineus is a conopid fly that can often be found crouched on knapweed flowerheads waiting for a bumblebee to land:

The Conopid fly Sicus ferrugineus
These are parasitic on worker bumblebees, but although I saw a good number of Bombus pascuorum workers today, none of them landed near the fly.

Leucozona glaucia is one of the most colourful hoverflies that we have. The combination of blue abdomen, yellow scutellum and shiny brown thorax is quite striking.

The hoverfly Leucozona glaucia
I caught a few glimpses of its duller relative, Leucozona laternaria, which I hope to show soon.

Sawfly larvae can be distinguished from moth and butterfly larvae by counting the number of prolegs. But I can generally pick them out quite quickly by their very round-shouldered appearance:

Sawfly larva on Ribwort Plantain
This close-up shows the semi-translucent nature of the body:
Close-up of sawfly larva
I went through the checklist of sawfly larvae and their host plants, but the only one specific to Ribwort Plantain doesn't match. That probably makes it a generalist polyphage, so the only way to find out what species it is would be to breed it through and identify the adult.

Caddis Flies are often mistaken for moths, especially when they come to light at night. The main distinguishing feature is the forward-facing antennae (although some of the longhorn moths also have this feature, in which case the Caddis Flies are recognised by their almost parallel antennae). This specimen is a female, identified by the greater number of jointed segments (5) in her mouthparts:

Caddisfly, member of the Limnephilidae family
That's the first Caddis that I've seen nectaring.

Caddis larvae are aquatic, living inside a case made from stones, shells, twigs or leaves, so the adults are usually seen close to water.

The Great Diving Beetle is also aquatic, and I found this one lying dead near a dried-out puddle:

Great Diving Beetle

The Angelica is already running to seed, so I suppose I might have another two weeks of it left. It's certainly a major source of nectar for insects, and I found hundreds of hoverflies, dungflies, sawflies and other assorted insects nectaring on it today. This ichneumonid caught my eye, due to its very long ovipositor:

Ichneumonid on Angelica

Thursday, 18 August 2011

Fungus time again

With all the rain we've had this year, I rather suspect we're going to have a good year for fungi: I'm seeing a few on the verges and in my garden, and yesterday I found this season's first specimen of Entomophthora muscae on a hoverfly. In my previous post, I mentioned that the Taphrina fungus alters the growth of the Alder for its own benefit by creating a large surface area for spore production and dispersal. This ability to alter a host for their own benefit is a recurring theme with fungi, and I never cease to be amazed at the lengths they go to in order to achieve this aim.

Entomophthora muscae is a fungus that uses flies as a tool for its spore dispersal. The fungal spores are ingested by the fly and the fungus rapidly grows inside the fly's abdomen. Eventually, the pink fungus breaks through the structure of the abdomen and becomes visible for a couple of days before it breaks down and the spores are released.

This is the shot of the hoverfly from a top-down perspective:

Hoverfly killed by the fungus Entomophthora muscae
The pink fungus can clearly be seen emerging from the abdomen of the hoverfly (which, unusually, is a Platycheirus species: Melanostoma scalare is the most frequent host in this area).

Two aspects of this photograph are of critical importance:

1) the hoverfly is at the very top of the plant (Ribwort Plantain)
2) the wings of the hoverfly are fully extended in an unusual forward-facing configuration

Both of these features will allow maximum airflow over the fungal mass and, more importantly, both are caused by the fungus. Before the fungus kills the fly, it causes it to move to the highest available point and then open its wings to the fullest extent. Then it kills it.

This ability of the fungus to control the fly's movement and configuration for its own benefit is astonishing enough, but it works with different flies from different families, so the fungus has found a way to control the movement of a whole range of different fly species.

Another feature of the configuration control is shown in this side view:

Side view of the fungal mass

The legs have also been fully straightened: yet another part of the configuration that maximises spore dispersal: truly amazing.

The fungal mass will break down and release spores over the next couple of days, leaving just a skeletal husk of the hoverfly on the plant.

It's not only nectaring insects that benefit from the Angelica. This is a shot of the miner Phytomyza angelicastri on the leaves:

Leaf-mining fly Phytomyza angelicastri on Angelica

The Rosy Rustic moth pupates underground until August, and this pristine specimen was resting on a low-level Dock leaf, so I rather suspect it had just emerged.

Rosy Rustic moth


Tuesday, 16 August 2011

Small gaps

The rain is still more or less continuous, with very short gaps between showers, and I have had to adopt a new tactic for getting some pictures: I watch the sky to the southwest and wait until I see a gap in the weather some 12-15 km away. I then rush out and hope to reach the fringes of town before the gap in the rain reaches me. That means I'm in place when the temporary stop occurs. This is fine for getting photographs of plants and mines, but not so good for insects because it takes them a little while to realise that the rain has stopped and they have warmed up enough to fly to the nectar sources that I'm watching at the moment.

Tufted Vetch is an odd plant: it grows in only a few places on my patch, but wherever it grows it is rampant. There appears to be no similarity amongst the places it chooses and there are places that appear to be ideally suited, but the plant is absent. It must have some very particular micro-climate requirements.

Tufted Vetch
A few more late summer portraits:
Knapweed or Hardheads

Red Bartsia

Devilsbit Scabious

Taphrina alni is a parasitic fungus on female Alder cones:

Taphrina alni gall on Alder
The tongue-shaped growth reaches 4-5 cm. long and turns red before releasing its spores. Note that the growth is caused by the fungus, but is made by the Alder tree for the benefit of the fungus.

Alder is a good food source for Sawflies: these are multiple mines of Acidia cognata. The broad-shouldered larva can be seen in each of the mines:

Mines of the sawfly Acidia cognata on Alder

This next shot shows just how attractive Angelica is for insects at this time of year. I counted 7 ichneumonids, 2 sawflies and 2 dungflies on this flowerhead:

Angelica with Ichneumonids, Sawflies and Dungflies

One of the few Ichneumons that can be identified by sight: Amblyteles armatorius, which is parasitic on larger moths.

Ichneumon Wasp Amblyteles armatorius

Harvestmen are related to spiders, but they don't make a web. They hide instead in plants, waiting for some unsuspecting insect to come wandering along.
Harvestman Mitopus morio on Angelica
I like how the Angelica echoes the shape of the legs.

The social wasps are divided into two main families: Dolichovespula and Vespula. Dolichovespula species (Dolichovespula sylvestris shown) can be readily identified by the 'malar space', which is indicated by the arrow below:
Dolichovespula sylvestris, a Tree Wasp
The malar space is the distance between the lower edge of the eye and the upper edge of the mobile mandible, or jaw. In Dolichovespula sp., the gap is large, making the face very elongated, whilst in Vespula sp., the gap is virtually non-existent. Most of the wasps that can be seen moving leisurely over Angelica at the moment, including the one above, are males.

The Potato Capsid, Closterotomus norwegicus, is commonly found on Knapweed and other composite flowers. I have never found it on potato:
Potato Capsid on Knapweed

Wednesday, 3 August 2011

Every cloud

The weather has been abysmal for several days, with bad light even when it has been dry. Today I saw blue gaps in the cloud, so I ran for the hills, where the Angelica is abundant.

This hoverfly got me rather excited, because I knew I hadn't seen it before. Several shots were rattled off and anticipation was high during the rest of the photography session. When I got the pictures back to the computer and opened the books, I was slightly disappointed to discover it wasn't a new species for me, but merely a new colour variation of one that I had seen once before. It's the orange and black version of the bumblebee mimic Eriozona syrphoides.

The bumblebee-mimicking hoverfly Eriozona syrphoides
Eriozona syrphoides is the only bumblebee mimic to have an obtusely re-entrant (curved) vein at the position indicated by the arrow.

Note. I have amended the identification of this hoverfly as a result of a much better set of photographs taken a few days later.

Here's a shot of it beside an ichneumonid:

Eriozona syrphoides (right) and ichneumonid (left)

Staying with ichneumonids, this one has a quite impressive ovipositor:

Ichneumonid with long ovipositor
I saw a few of those wandering over Knapweed flowerheads, so we know what that ovipositor is used for.

This large brown specimen looks to be close to the Ophion family:

3 cm. ichneumonid

Dungflies are voracious hunters as adults (they're probably making up for all the dung they eat as larvae.) This one is making a meal of a smaller sawfly:
Dungfly with prey
But this dungfly has fallen foul of a little cream-coloured spider:

Spider with dungfly as prey

Now that's a truly vicious circle.

I was quite surprised to find a pristine Red Admiral butterfly nectaring on the Angelica:

Red Admiral butterfly
It's absolutely pristine, with no wear whatsoever, so it's clearly one of the local offspring of the early summer migrants. These feed solely on nettles as caterpillars.

At this time of year I always look closely at clusters of aphids on Knapweed. The larvae of the hoverfly Syrphus ribesii consume large numbers of aphids, and the female always makes sure her offspring have an adequate supply:

Larva of Syrphus ribesii with aphids

Meliscaeva cinctella is one of the later hoverflies, usually to be found from August onwards. Its larvae are also aphid eaters, but solely on tree-dwelling species, such as the Wooly beech aphid.

Meliscaeva cinctella hoverfly

Fairy Flax is a very delicate little flower which I tend to find near the edges of forestry, or along forest paths:
Fairy Flax

Just as I was getting out of the car, this leafhopper flew over my shoulder and landed on the path in front of me. Click.
The leafhopper Cicadella viridis