Sunday, 30 September 2018

Small Chinamark tubes in Undy

Keith Jones, from Undy, sent me this photo and fascinating email.

On the 16th of August I noticed that my pond, which a few days before had been covered with duckweed, was almost completely clear of the plant. On looking more closely I noticed a number of tubes that appeared to be made out of duckweed leaves and these tubes were moving slowly about on the surface of the water although there was no wind to cause the movement, meaning that there was something in the tubes causing the motion.
At first I thought of Caddis fly larvae that build tubes to hide in but I thought they usually crawled about on the pond bottoms not on the surface. I didn't do any more about the puzzle of what the tubes were at once but a few weeks later I read that Small China-mark larvae fed on duckweed and then a few weeks later still I looked the moth up on ukmoths and discovered that the larvae build little tubes - so the mystery was solved.
Checking the two photographs I took at the time of parts of my small pond (c 2m by 1.5m) I counted over 150 of the tubes so there must have been well over 300 in total!

This was followed soon after by an email from Keith discussing both the abundance of Cataclysta larvae and their subsequent rapid disappearance:

A few days after I took the photographs of the tubes I noticed that most of them had gone, which I assumed was due to a number of possible reasons
- they had been predated
- they had pupated
- they had all died through lack of food
- or a combination of these
Under normal circumstances, in say a reen or ditch full of duckweed, the larvae would be hidden from view munching away at the duckweed leaves while camouflaged by their tubes.
In the case of my pond, however, there may have been so many larvae that they had eaten all the limited amount of duckweed leaving their tubes out in the open in plain view where I happened to spot them.
So which of my possible reasons for their subsequent disappearance is the correct one?
I rule out the first because there are no fish in my pond which might eat them although there could be some other predator.
I'd like to think it was the second one but that it was most likely the third one with any surviving larvae scavenging the tubes of the others until all were gone, or....

Wednesday, 26 September 2018

Magor mines

An unsuccessful search for Alder fungi at Magor Marsh allowed me the chance to record a few leaf mines.  Phyllocnistis saligna were abundant on Crack Willow, Acrolepia autumniella was making blotches on Bittersweet, and there were 4 common species mining Hawthorn.  I checked a lot of Meadowsweet because the only time I have seen the scarce Stigmella on that plant was at a wetland in Glamorgan where Meadowsweet was allowed to grow ungrazed and uncut.  After seeing a lot of Agromyza fly mines with very sparse frass, I was pleased to spot one mine of Stigmella ulmariae (S. filipendulae now) new for VC35 with a broad line of black frass.

 I made my way over to a group of Aspens, which supported the leafmining fly Aulagromyza tremulae plus a few small tentiform mines with underside creases.  I hoped these might be Phyllonorycter sagitella, but the mines seem much too small and I now think they are Caloptilia stigmatella.  I subsequently disturbed an imago of C. stigmatella about 50m from the Aspen group.

Sunday, 23 September 2018

Mid September moths

Several warm nights recently have produced 25 to 30 moth species at the Dingestow Court MV, although there has been a lack of headline species, especially migrants.  Highlights were:

15/9 Autumnal Rustic, Brown-spot Pinion (not found at Dingestow until 2016) and Large Wainscot

16/9 late Single-dotted Wave & Mottled Rustic, Eudonia pallida, Crocidosema plebejana (4th Gwent record) and Acrobasis consociella (much rarer than the similar Trachycera advenella)

17/9 Barred Sallow, Maiden's Blush, Dark Swordgrass and Tinea semifulvella
19/9 Red Underwing, Brown-spot Pinion and Ypsolopha sylvella (last seen in VC35 in 2005)

21/9 Blair's Shoulder-knot and a fresh Willow Beauty

Tuesday, 4 September 2018

Oak Lutestring

Oak Lutestring (Cymatophorina diluta) in Tintern on 28th August was new to the garden and completes the full set of Thyatirids for the site. A further three specimens of diluta have subsequently been recorded, including one last night (3/9).

Monday, 3 September 2018

Deja vu

Another Heath Rustic wandered to Dingestow on 2/9/18, accompanied again by lots of wasps and a good range of other insects.  A Lesser Stag Beetle was non-lepidopteran highlight, whilst good moths among the 63 species (a good total for September) included a 2nd generation Waved Umber, Dingestow's second Wood Carpet (I think), 2 Broad-bordered YU, an early Satellite, 3 Pale Eggar, Eudonia pallida, Ectoedemia louisella, 2 Endothenia marginana, a miniscule Stigmella atricapitella (gen det male) and a small Depressaria that I need to check.  The previous night was a little less productive, but a Mouse Moth and a 2nd generation Buff Ermine were noteworthy. 


The abundance of Centre-barred Sallow this year has been commented on by Ian Rabjohns and by a couple of Carmarthenshire moth'ers; I caught 15 on 3/9, beating my previous site records of 10 on 6/9/16 and 4 on 5/9/2004.