Nercwys Forest

A good circular walk here, which I think Toby really enjoyed!

Walkers need to go clockwise to face the cyclists using this anti-clockwise route.

Scolioneura betuleti  (Klug, 1816)

Eastern Bod Petryal

A short morning amble up past the white house in Fron Wyllt. On one of the Wych Elms, Ulmus glabra, there was a long, quite tubular Phyllonorycter mine, very much between two veins. suggesting the Elm Midget, Phyllonorycter tristrigella (Haworth, 1828). This one was showing only limited edge damage to the upper epidermis, as though it perhaps hadn't fully developed. One possible exit hole.

The mining is carried out in July and then in September/October. This one is presumably from the first generation of 2019?

It was unlikely to be Phyllonorycter schreberella, as this is an oval and less contracted mine, possibly across main veins. In addition this is less rarely found on Wych Elm, and also it is commoner in the south of the country (England and Wales), although the distribution certainly does reach North Denbighshire.

Interesting afternoon walk to the east across the Afon Clwyd, along a made track and down a path along the east track, then up through the spruce forest, and back along the Fisheries Road to the main Cerigg-y-drudion road - taking care to take to the verges to avoid the speeding cars.

Bod Petryal in the drizzle

Plenty of Mompha raschkiella mines on the Rosebay Willowherb along the circular path around Bod petryal. Apparently this is the only leafminer found on Rosebay, while there are a range of  other Mompha species on the true Willowherbs, Epilobium. 

The larvae can be found from the end of May to the end of July and from the end of August to the end of September.

The tunnels loop around cutting off tissues (until tissues turn reddish) a large yellowish patch mine is formed.

Fron Wyllt again

Interesting afternoon walk at Fron Wyllt, taking a quick look at the Beech leaves, Fagus sylvatica, on the trees which appear to be planted near the car-park, on both sides of the river. Toby is definitely gradually getting more used to my no-doubt boring stops to look at leaves!

I found about half a dozen relatively short Phyllonorycter mines which seemed to have a strong central crease. Some of these seemed fairly old and abandoned. This would fit in with Phyllonorycter messaniella, which seems to fold and distort the surface of the leaf quite strongly in most of the pictures shown. I saw one particularly long mine, still apparently with a central crease, but there are photos on the internet showing equally long mines that are identified as P. messaniella. These mines could be up against the midrib, or they could be away from it, mostly half way out towards the margin of the leaf. 

However the other possibility is a highly contracted long tubular mine which is said to have several pleats but these might look like just one, and I found three of these, two side by side on one leaf? So Phyllonorycter maestingella was confirmed, and I will come back to this later.


Phyllonorycter messaniella

Phyllonorycter messaniella (Zeller, 1846), Zeller's Midget, is also known as the Garden Midget - arbitrarily? 

According to UK leafmines, the mines are generally active in March - April, again in July and then October, although these dates seem rather tenuous (?). Perhaps its July to October? They don't really fit in with the idea that the third generation only occurs overwintering on the evergreen Holm Oak, December to March. On Beech and Hornbeam this species is said to be found on the lower surface between two adjacent veins, with a sharp fold.

Another more detailed description from the excellent Bladmineerders website is "oval, lower-surface tentiform mine, 9-14 mm long, mostly between two lateral veins. The lower epidermis with a single sharp fold (sometimes forked near its end). Pupa in very flimsy cocoon, that contains a bit of frass laterally and at the rear end".

Polyphagous on woody plants, not uncommon on Beech. However, the Dutch view is that the main host is Oak, although I haven't looked for it there yet. 

It was accidentally introduced into Australia and New Zealand, where it turns out to be regarded as a pest, mainly (and initially drastically) on introduced oaks, etc, but including on members of the native Southern Beech genus, Nothofagus. Initially it ran riot in New Zealand with an average of many mines per leaf until European parasites were introduced, when some degree of control was developed as would be found "naturally" in Europe. 

Phyllonorycter maestingella

The significantly longer mines on these leaves belong to this species, the monophyletic Beech Midget (Muller, 1764). The several folds may appear as one, and the silk is strongly contracted, often leading to a tubular appearance.

It has two broods, the adults flying late April to June, and again in August. The mines are therefore usually active in July and September to October. The insect then hibernates as a pupa, presumably on the ground.

Agelastica alni, by golly

Walking through the pretty woodland nature reserve of Fron Wyllt, I looked at the leaves of some Alders by a small bridge over the rapidly flowing stream.

On the first day I noticed that they had been a bit frazzled.

On the second day I actually thought about it, and wondered whether they were sawfly/slugworm larvae that might be responsible. It sort of occurred to me (very slowly) that I might not have seen this damage on Alder before. It looked a little like the shredding or skeletonisation of beetle larvae damage (as I have seen regularly on Viburmum in recent years) or slugworm damage (as I have seen in the past on Birch). Eventually I found a larva which I thought I recognised as a slugworm style of sawfly larvae. A nasty-looking glossy black caterpillar.

When I got home I saw references to Alder Sawfly, but that is white and spiky, so it was not that. By chance I came across many US references to an Alder Flea Beetle with very similar larvae and blue adults. But this apparently doesn't occur in Europe. I was now intrigued and I finally came across references and photos relating to Agelastica alni, a beetle thought to be possibly extinct, but rediscovered and apparently spreading across several parts of the UK. Oddly enough, it looks very similar to the Flea Beetle from the US.

Here is a photo of a larva on apparently fresh damage, near the base of the leaf.

And another, with slightly older damage,

Here is a photo of older damage, no larva seen.

And a photo of skeletonised leaves against the sky, indicating what potential damage could be done to the Alders along our streams and rivers.

This is the site where the worst damage was seen,

Ganoderma on Horse Chestnut by the Meanders Bridge, near Hope Farm

 A nice cross-section of the conk, hopefully the right way up:

The tree is not looking at all well, with badly cracking bark:

Alder leafmines

Phyllonorycter klemannella, (Fabricius, 1781), the Dark Alder Midget 

The first and possibly much the commonest mine I found today was Phyllonorycter klemanella (=kleemannella), the Dark Alder Midget. I was only looking on a few lower branches of an alder on the north side of the Bourne opposite Easterfield Bungalow.

These mines were both away from the midrib, and also close to the midrib. They showed no strong creases (so the mines were not Phyllonorycter rajella, larvae June and July), and it is the right time for the second generation of these larvae in the year, July- August. The mines were not long and thin enough to be confused with Phyllonorycter froelichiella, which is also un-creased, but with grey larvae, usually a bit later in the year, such as September-October. All these are underside mines on Common Alder, as opposed to Phyllonorycter stettinensis, which is strongly creased, characteristically yellow-green and on the topside of the leaf over a vein, larvae May and July-August but can be as late as November.

There were active green fresh mines but there were also other older mines, some emptied, which might have been from the first generation, May-June, or already-hatched mines from the second generation. Here is a supposedly typical fresh oval mine of Phyllonorycter klemanella (=kleemannella). 

Here is another mine, from the upper side of the leaf.

Phyllonorycter stettinensis (Nicelli, 1852), the Small Alder Midget

I did also find two, or a few more, examples of Phyllonorycter stettinensis, on the upper side of the leaf. This is yellow green, with one strong central crease, the timing is right for the second generation  but in this photograph it is NOT over a lateral vein, as described in Bladmineerders. A second mine was over a lateral vein, so that is OK!

This mine is apparently much more typical, over the vein,

Phyllonorycter froelichiella (Zeller, 1839), the Broad-barred Midget

I may have found one or two examples of this leaf-miner, but it is a bit early for this particular species. Also this particular mine does look as though there is the start of a single crease in the mine, which would be unexpected in froelichiella, so maybe this is a misidentification. With this crease it could be rajella.

I need to check back, but I don't seem to have ever seen froelichiella for sure - I will check through as much as I can.

.Phyllonorycter rajella (Linnaeus, 17589), the Common Alder Midget

Why haven't I found this species on the leaves of this tree? The larvae should be found in June/July and more in September/October, and I would have expected to find it by now.

Heterarthus vagans ( ), 

This is a possible, but not definite, identification,