Late in Dene Park

A few mines about in the gloaming, getting a bit difficult to see!

On the Beech there were a few fairly long thin mines, all apparently deserted (!) of the Beech Midget, Phyllonorycter maestingella (Muller, 1764). I do wonder why this year I find so few occupied mines of this species, and I do seem to find more mines of P. messaniella on Beech, with its wider host range.

Access Trail

Wandered along the shaw on the normal Bourne walk as the light faded this evening, I looked at one of the small Field Maples at the far end and found a few few folded down leaf lobe tips. I wasn't sure whether these folds indicated a Caloptilia as I had first thought, or possibly Phyllonorycter acerifoliella (Zeller, 1839), the Maple Midget. In the end I think at least one leaf tip roll turned out to be the latter, although the revealed mine proved to be empty.

It is regarded as common with the mines occurring in July (presumably this one, hence emptied, with an exit hole) and October.

Eight Mallards overflew in a group. Not much else around, as it was getting very dark.

Fox Covert

Back to Dene Park, and diverting off to Fox Covert and the field beside it.

At the top of the field I found a few small folds at the tip of the lobes of Sycamore leaves, which I thought might be indicative of a Caloptilia species. This could be the Small Red Slender, Caloptilia rufipennella, found in the UK since the 1970s. The moth over-winters, perhaps in an evergreen such as Yew and reappears about spring. The mines are formed in sycamore leaves around, first as a small mine tucked into a vein axil, and you then get usually 3 "leaf tip folds - cones?" of increasing size in which the larvae continue to feed.

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.