Stuart1960's picture

Unknown moth

Observed: 30th May 2011 By: Stuart1960
unknown moth
Description:

about 3 cms in length

Identifications
Species interactions

No interactions present.

Species with which Minor Shoulder-knot (Brachylomia viminalis) interacts

Comments

DavidNotton's picture

minor shoulder knot

light grey colour and darker grey patch on costa near apex fit minor shoulder knot better. Rustic shoulder knot is browner

DavidSlade's picture

Stigmata

The orbicular stigma looks rather elongate rather than the nice round one you get in Minor Shoulder-knot. There's no sign at all of the claviform stigma. It just doesn't look right to me.

DavidNotton's picture

minor shoulder knot

Yes the orbicular stigma is elongate, while it is usually round, an elongate stigma occurs in a proportion of minor shoulder knots. The claviform stigma is worn off as the fore wings are abraded in this region, as is the middle of the thorax.

DavidSlade's picture

Unconvinced

Sorry David, but I still don't see this as Minor Shoulder-knot. Apart from the thorax and a bit off the end of one wing this moth does not look that worn to me. I still see more Apamea sordens than Brachylomia in it.

DavidNotton's picture

Significant wear

There is significant wear on the wings in the area of the claviform stigma, this is clear because the pattern is asymmetrical in places because one wing is more worn than the other; the cilia are worn too, as is the thorax and the chip out of one wing.

It certainly isn't sordens because the ground colour is wrong.

Arguing that it is sordens but not viminalis because you can't see a claviform stigma is a fallacious argument - sordens has a claviform stigma too, so your own argument would discount sordens too.

So the evidence as I see it is as follows:

light grey ground colour = viminalis NOT sordens
grey patch near wing tip = viminalis NOT sordens
oval orbicular stigma ok for either species
missing claviform stigma through wear = no evidence for any species.

This is consistent with viminalis, and not sordens.

DavidSlade's picture

but...

To quote from MBGBI:
"Forewing glossy, pale brown with greyish or reddish tint; lightly mottling in a darker shade; a conspicuous undulating black basal streak; reiform stigma slighlty paler than ground colour, very narrowly outlined white; orbicular stigma concolourous, inconspicuous; cross-lines paler than foreground, crenulate, inconspicuous, subterminal with a feint dark mark basslay at the costa; termen with a series of small black interneural crescents; fringe greyish brown with pale line at base"

or
"Forewing greyish white; basal streak short, black, slightly widening distally, often bordered costally by a narrow ochreous line; before antemedian line a short oblique subcostal streak; antemedian line twofold grey or blackish, inner part often incomplete; median fascia slightly more grey than wing base; post median line blackish, with median tooth forming proximal margin of reniform stigma; subterminal line pale greyish white, obscurely bordered ochreous white proximally; terminal line black; upper stigmata of ground colour or ochrously tinged, incompletely outlined black; claviform stigma black, linking the ante- and postmedian lines to form a an H mark; cilia of ground colour."

I don't see this a grey moth with black markings, I see a pale brown/grey moth with inconspicuous markings. The thorax is brown, not grey. It's a bit worn, but not to the extent that all the diagnostic features to have been removed - I can see the antemedian & postmedian line on one wing, but no linking line, I can see the terminal cilia on one wing and it has a pale base, not conncolourous with the ground colour.

I am happy to accept that it may not be Apamea sordens, but I am not happy to accept that this is Brachylomia viminalis. What I can see simply does not fit. As I said in my original suggestion, it has more the feel of an Apamea to me.

DavidNotton's picture

not Apamea sordens

I agree it's not Apamea sordens.

Quote any description, but if the specimen is worn it's necessary to work on the characters that remain. Absence of evidence is not the same as evidence of absence.

DavidSlade's picture

I quoted the description

I quoted the description because it highlights a couple of issues.
Firstly, ground colour:
Apamea sordens:pale brown with greyish tint.
Brachylomia viminalis: Greyish white.
You see a grey moth, I see a pale brown one, so we're not going to agree there.

Basal Streak:
sordens:Conspicuous undulating black
viminalis: short, black, slightly widening distally
Nothing in it there

Reniform stigma:
sordens: slighlty paler than ground colour, very narrowly outlined white
viminalis: ground colour or ochrously tinged, incompletely outlined black
It certainly looks paler than the ground colour to me, and I can see a white outline

Orbicular stigma:
sordens: concolourous, inconspicuous
viminalis: ground colour or ochrously tinged, incompletely outlined black
The descripion doesn't mention the shape which is spot on for all sordens whereas you say it is right for a proportion of viminalis. We'll have to agree to differ on that one.

Crosslines:
sordens:paler than foreground, crenulate, inconspicuous, subterminal with a feint dark mark basaly at the costa
viminalis:antemedian line twofold grey or blackish, inner part often incomplete, post median line blackish, with median tooth forming proximal margin of reniform stigma
You say these have all worn off, I say they are there and consistent with sordens.

Treminal line:
sordens: a series of small black interneural crescents;
viminalis:terminal line black
Ok, that doesn't give the full picture as viminalis has dashes, not a full line, but these dashes are longer giving a black line with pale gaps rather than the short black dashes of sordens.

Terminal cilia:
sordens: fringe greyish brown with pale line at base
viminalis: of ground colour

You suggest we work with what is there and not what is absent, and that is a fair point (I wsh I'd never mentioned the claviform stigma). You also said that there were more characters consistent with viminalis that sordens, and this is the point that I dispute. I see plenty here to convince me that it is Apamea sordens, and nothing of Brachylomia viminalis.

DavidNotton's picture

This is going nowhere

I am happy to accept that it may not be Apamea sordens.

I see plenty here to convince me that it is Apamea sordens

DavidNotton's picture

This is going nowhere

I am happy to accept that it may not be Apamea sordens.

I see plenty here to convince me that it is Apamea sordens

DavidSlade's picture

Nowhere?

The point was that I would be prepared to accept an alternative determination if one was offered.
You wanted me to look at the characters that are available, and in doing so I have convinced myself it is not Brachylomia for the reasons I have stated, and restored my faith in my initial gut feeling that it is Apamea sordens.

DavidNotton's picture

Ok

you have a different interpretation, that's fine, I just don't think we are going to agree. That's life.