I had the two large Dioryctria species moths illustrated below to light in the Chilterns last night but separating them on sight can be quite difficult as the characters are open to a certain amount of "interpretation", especially when they're a little bit worn as both of these were. The first has a wing length of 18mm, the second is 17mm.
I'm reasonably sure that they are Dioryctria sylvestrella (top) and Dioryctria abietella (bottom) but I'd welcome any other views. The two areas to look at, so we're told, are the amount of brown in front of the central cross line and, particularly, the shape of the final cross-line before the dorsum. D.sylvestrella has a more extensive area of brown and the final cross-line has relatively smooth curves, while the brown on D.abietella is less prominent and that final cross-line is more jagged in appearance.
Dave Wilton Westcott, Bucks
I notice on the Norfolk moths website there is a diagram showing how the overall angle of the subterminal line is different. In addition, the sub-terminal line approaches the dorsum almost at a right-angle in D. sylvestrella. It looks as if this is further evidence to support your (and my) identification.
ReplyDeleteOn another matter do you know why the Northumberland moths website does not seem to be available? I am visiting Northumberland later in the month.
For distinguishing between the species, I am not sure how useful is the amount of brown before the first cross-line, unless you have them both side-by-side as here. The smoothness of the subterminal line seems to be easier to distinguish (as someone who has only ever seen photos!).
ReplyDeleteIn regards to the Northumberland moths site, I can add that it has been down for at least 3 months, when I started to research a trip to the North Pennines which I made in June.