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.