Sunday, 30 August 2009

Who would be a sawfly?

Each time I look at the Nematus pavidus larvae I seem to see a different predator. This Flower Bug - Anthocoris nemorum - wandered into the area of leaf where the sawfly larvae were feeding, picked up this specimen and carried it to the edge of the leaf where it began to consume it.


The area of leaf shown is about 8 mm x 6 mm.

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I update my species list in batches: it's more convenient that way. During yesterday's update, the list passed a new milestone: I now have 1302 species on the list, 7 of which are new to Ireland and dozens are new to Co. Donegal.

Friday, 28 August 2009

End of a Sawfly

The other day I showed the Shieldbug Picromerus bidens, which are predatory on caterpillars. This shot shows a sawfly larva being consumed tail-first by another specimen. The larva is about 3 cm. long and is suspended from the proboscis of the Shield Bug.


The original shot is much higher quality, but for some reason (speed?) Blogger always drops the quality of images.

Thursday, 27 August 2009

More Nematus pavidus hatching

The batch of eggs that I showed yesterday is in the process of hatching:


A couple of things are worth mentioning, here: Firstly, sawfly larvae (in common with moth and butterfly larvae) go through a series of skin moults, after which they may change colour. These different colour forms are called 'instars'. The instars may vary in colour and/or in pattern, leading to some difficulty in identification, since all instars need to be known for a positive identification in each case. Some of the sawfly larvae in the above image have just started to eat and have turned green, the expected 1st instar colour for this species. The larvae which have eaten only the eggshells are still pale and are really instar 0 larvae.

Also note the marks (top left) where the eggs were attached. These indentations are used to anchor the eggs, and are made by the modified ovipositor, or saw, of the female, which gives rise to the name 'Sawfly'.


Despite the more-or-less continuous rain, a few moth species are still coming to light.


This is Lesser Yellow Underwing - Noctua comes - and is new to me.


And this is Dark Marbled Carpet, which I see every year.

Wednesday, 26 August 2009

Nematus pavidus

Those of you who have been following my exploits will know that I have been following the larval stages of the Sawfly Nematus pavidus for a few years.

To summarise very briefly, the larvae appear around this time of year in large batches, and consume vast swathes of Willow leaves, defoliating entire branches. During that time they are visited by parasites and predators of all kinds, with secondary parasitisation taking place. I tend to follow the life-cycle very closely, and keep a photographic record of what I see, so today is day 1 of that process for 2009.

The eggs are laid in batches on the underside of the leaf:

You can clearly see the single ocellus (eye cell) of the larva inside the egg, which is about 1mm long.

The larvae hatch out and spread over the surface of a single leaf:

Notice the characteristic s-shape of the larvae, which are about 2mm. long at the end of day 1.

When I took the shots, I had no idea that surprise number one was already waiting for me. When I got the pictures onto the computer, I spotted this truly minute (1 mm!) parasitoid exploring the larvae:

Based on size and shape, I'd venture that this is one of the Chalcids (parasitic wasps, related to Ichneumonids). So already we have something new for this increasingly interesting project.

The orange spots are a fungal rust.

While I was taking the shots of the larvae, I spotted this Chironomid (non-biting midge) wandering over the leaves:

Monday, 24 August 2009

Biter bit, part 2

I've previously explained how Tachinids are parasitic on larvae of moths and butterflies. This shot shows a Scathophaga Dungfly with a Tachinid as its prey. And so the food chain continues.


I found this dead Cicadella viridis on a grass stem. My eyes were drawn to the open-wing configuration and immediately my fungal radar kicked in. It turns out that several species of the Entomophthora family are parasitic on leafhoppers, so the research continues.


I'm pretty sure I can see signs of pink fungus appearing between the abdominal tergites.


I'm not quite sure what's going on with this Carder Bumblebee. Its baskets are empty, and it is moribund (and wet!). Maybe the hive has run its course for the year.


This is Neuroctena anilis, a snail-killing fly. In common with most other parasites, its flight pattern is quite distinctive, with lots of controlled hovering as they search for hosts for their eggs:


This specimen of Frosted Orange moth is a little early, which is pretty surprising, considering how cold and wet it has been for the past 40 or so days.

Friday, 21 August 2009

The urge to reproduce

I never cease to be amazed at the attempts of disadvantaged plants to reproduce. This tiny (5 cm. tall) Knapweed had managed to produce viable flowers despite having seeded in the middle of a road.


This Willow had been damaged much earlier in the year, and the new shoot has a catkin on the end of it:


I suppose the urge to make offspring is an essential part of the make-up of any successful species.

This blue Sawfly is quite numerous at the moment. The curved antennae - somewhat reminscent of horns - are quite distinctive.

Tuesday, 18 August 2009

Biter bit

Harvestmen are related to spiders, but are different in that they have no 'waist' in the main body, and they don't make webs: they tend to lurk on leaves and flowers and leap out on their prey. This is Mitopus morio, with accompanying phoretic mite. I'm not quite sure why these mites are so brightly coloured, but I suppose if you're harmless, then you don't have to hide.


Here's a closeup:

For the last 7 years I've been photographing my local wildlife and at the start I wandered around finding opportunistic shots. I still take shots of whatever I find, but I also find more interesting shots if I target something, rather than be drawn here and there by whatever I see. I've been looking at ferns more closely this year, because I know there are related species that I haven't found (the leaf-miner from last week is a perfect example). Here's another:

Notice that the spore-bearing sori of the Male Fern - Dryopteris filix-mas - have been scraped off and gathered together in a pile in the centre. That 'lump' is the home of the larva of a micromoth, probably one of the Psychoides sp. I'll need to breed it through to see what emerges.


Tonight's opportunistic shot is the Spined Shield-bug - Picromerus bidens. These have just reached adulthood after going through a series of nymph stages: a feature in common with all other bugs.
I find these quite numerous, but only in very tightly confined environments: where bog meets woodland fringe.

Thursday, 13 August 2009

Rare gap in the rain

I was surprised to see this Wood Mouse - Apodemus sylvaticus - out and about during the daytime. Although it didn't like me to move, if I sat still it wandered around eating seeds quite happily.


True bugs form a large percentage of our insect species, but they are understudied and under-documented. This is one of the Mirid bugs, Closterotomus norwegicus, also known as the Potato Bug.


While photographing moths at light, I was surprised to find this hoverfly crawling up the wall. It's Eupeodes corollae, which has been seen mixed in with huge migrations of 7-spot ladybirds on the east of England this past week.

Tuesday, 11 August 2009

Ancient Deciduous Woodland - Fungi

Many fungi are dependent on the trees that grow in deciduous woodland, and some species need that woodland to be hundreds of years old. This is due to the fact that some fungi are successional, only appearing when another fungus has already been present for some period of time and has created a suitable environment for the dependent fungus. As a result, it is a general rule that the older the woodland, the more species of fungi will be encountered, with some of the rarest species only being found in truly ancient woodland.

No great rarities on show today, but I found a rather nice example of the Tawny Grisette - Amanita fulva:

Note the volval sac at the base of the fungus, looking rather like an egg shell. This is a good indication that you're looking at an Amanita. It's pretty important to identify this family, because many are toxic and some are deadly poisonous. Amanita fulva is said to be edible, but best avoided due to possible confusion with other, more dangerous, species. I won't be trying it.


Russulas are readily identified due to their brightly coloured cap and the pure white, chalky stipe (stem). This single specimen of Russula lutea was growing under Beech. Mycologists are usually reluctant to name Russulas to species, but this one is unusual in that it has orange gills, rather than the white or cream that we usually find on this family.



Russula maire
i - the Beechwood Sickener - is very common, and is always found under Beech. I find this one to be a bit of an anomaly: it is (violently) emetic for humans, but it is rare to find a specimen that has not been nibbled by mice or eaten by slugs or snails.


Oudemansiella mucida
- the Porcelain Fungus - is incredibly beautiful: photographs cannot possibly do it justice. This is also associated with Beech, but on the higher parts of dead branches.

The cap is extremely thin and translucent with a pearlescent gloss to its shiny cap. A few years ago, I found that the best way to illustrate part of its beauty is to take a shot from underneath:


Finally for today, the bracket fungus Ganoderma australis. Whilst it may not be primarily guilty of causing the death of a tree, it certainly means the end is close. A huge Beech near this one had several specimens growing on it, and last year it split down the middle, leaving one half standing and the other half lying horizontally.


This has the makings of a good year for fungi.

Monday, 10 August 2009

Ancient Deciduous Woodland

I have been looking for the Bracken leafminer Chirosia histricina for a few years, now. It's clearly very choosy about where it lays its eggs: A long stretch of Bracken was empty apart from a very shaded section under a Beech. Maybe they like tightly-controlled temperature or humidity.



One of my favourite hoverflies - Leucozona glaucia:



A much more developed case of the fly-killing fungus Entomophthora muscae:

I'm already seeing dead flies on most Angelica plants now. (The fungus is the orange/pink area on the abdomen).


The fungal season has started quite early this year, so I'll show the first images in the next post.

Friday, 7 August 2009

Murder most foul

I've been stalking a female ichneumonid laying eggs in larvae inside Knapweed seedheads for a couple of days.

First, she explores the seedheads to find one that is occuped - usually by fly larvae, such as picture-wing flies:

Then she flips the ovipositor out of its sheath (note that the sheath splits along its length):


Then we have the repeated act of positioning the ovipositor and laying the egg:


This process is carried out for a minute or so, then she moves on to explore other flower heads.

I stapled together a few photographs of the process into a video of sorts:

video


Here's a different species exploring Creeping Thistle:


The fungal season has started, so I'll be making some trips to older woodland very soon. This is what I've always known as Bolbitius vitellinus, but I seem to remember its name changed in the last year or two.

Another new micromoth: Acleris emargana, which is a feeder on Salix sp.

Identification updated 13/9/2011

Thursday, 6 August 2009

Good old Angelica

At the moment, I'm doing little else other than patrolling the Angelica plants: they'll be gone to seed soon enough.

A welcome return of one of the later hoverflies, Meliscaeva cinctella:

Ichneumonids of various colours and markings continue to nectar: every umbel has a couple.


The first (of many!) of this year's sightings of the effects of the parasitic fungus Entomophthora muscae. The fungus kills the female fly, after having forced her to climb to a high position, open her wings and extend her legs. This maximises the opportunity for spore dispersal once the fungus has erupted through the abdomen.


Traces of the pink fungus can be seen on the back of the abdomen, to the left. The spider's web is incidental, although the fly might well have crawled through it on her last journey.

Wednesday, 5 August 2009

Bad light

Even when it isn't raining at the moment, any light that we do get is horrible, but we do what we can.

The Angelica is currently covered with insects of all kinds. Most are nectaring, but a few of them use the nectaring insects as a source of their own food in a similar way that crocodiles and lions use watering-holes as prime feeding ground.


The above shot shows:

A) Ichneumonids
B) Tenthredo sp. Sawfly
C) Ectemnius Wasp
D) Tree Wasp

This nectaring Ichneumonid poses a bit of a problem. I've seen this upward-curved ovipositor a few times, but I can't really work out the purpose of that curve. Maybe it reverses into a hole and lays its egg backwards?


Sometimes you see something and you intuitively know it's new. This Leafhopper was a bit larger than the usual ones and slightly more rounded. A quick check through the references reveals that it's Aphrophora alni, and is new to me.


Similarly, this hoverfly shouted "I'm new, too", and I managed to get a few shots before it flew off. It's certainly a Melangyna sp., but that's as close as we can get without capturing it.


These are scarce at the best of times: the larvae are specialist eaters of specific aphids.

Saturday, 1 August 2009

Moths

I think moths must be the most problematic group I've encountered.

First of all, there are over 2000 species to consider. Then, as I've mentioned before, colour is generally much less important than pattern. We also have to factor in the fact that some species are extremely variable. Then, finally, we have to consider wear.

If you have an unidentified specimen in front of you and a reference book (or more than one book!), then just trawling through the images won't help very much. It's a matter of finding something that:

a) looks quite similar
b) has a phenology that more or less matches.
c) is a reasonable size.
d) has plant dependencies that match the location where the specimen is found.

Then you need to read the species accounts for the candidates, and see which of the critical separating characteristics are present. References to 'similar species' should also be consulted.

That should lead to an identification in perhaps 90-95% of specimens. The remainder might be too worn to sustain an identification, but we also need to then consider aberrations.

The following specimen has been identified (not by me!) to be Dotted Clay - Xestia baja.


The species account says: "The most conspicuous diagnostic markings are the two small, sharp black dots just below the leading edge, close to tip of forewing." Sadly, mine has only one "sharp black dot", and one blurred one. So when all else fails, we need to invoke Dunlops "fourth law of moth identification". Which goes something like this: "When a moth fails to satisfy the basic diagnostic markings of all species, we need to add in missing features one at a time to see if they lead us to an identification, as long as they don't conflict with the diagnostic markings of any other species." Which means that in order to identify all specimens satisfactorily, we need to know what all the rest look like, or might look like.

This might take some time.