Hi Alan, to identify Copper Underwing vs. Svensson's CU you need to turn the moth upside down and pull the hindwing out fully to look at its underside - the extent of the copper colour determines the species (see Field Guide). I find that I can only do this if the moth is briefly anaesthetised using ethyl acetate. It is said that another distinguishing feature is the colour of the palps (CU pale throughout; SCU only at tip), but I have not found this to be very easy to determine. Alternatively, on iRecord you can record these moths as the aggregate species.
As John says, the moth needs to be man-handled so that you have a clear view of the fully-extended hind-wing underside. These moths are very slippery customers but I usually manage it without resorting to an anaesthetic by first getting the individual facing up the side of a reasonable-sized pot. I then stick index and middle finger of my right hand over it (either side of the body) and slide it carefully up the side of the pot so that my thumb can go underneath the body. With the moth now pinned between two fingers and thumb, I can turn it over and open out the wings on one side with my left hand to inspect the amount of copper (the pictures in the field guide show what you are looking for). This takes a matter of seconds, after which the moth can immediately be released having only lost a few scales (most of which would be lost anyway even if you did use an anaesthetic).
It has long been accepted that markings on the palps are not a safe way to distinguish these two species.
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Hi Alan, to identify Copper Underwing vs. Svensson's CU you need to turn the moth upside down and pull the hindwing out fully to look at its underside - the extent of the copper colour determines the species (see Field Guide). I find that I can only do this if the moth is briefly anaesthetised using ethyl acetate. It is said that another distinguishing feature is the colour of the palps (CU pale throughout; SCU only at tip), but I have not found this to be very easy to determine. Alternatively, on iRecord you can record these moths as the aggregate species.
ReplyDeleteAs John says, the moth needs to be man-handled so that you have a clear view of the fully-extended hind-wing underside. These moths are very slippery customers but I usually manage it without resorting to an anaesthetic by first getting the individual facing up the side of a reasonable-sized pot. I then stick index and middle finger of my right hand over it (either side of the body) and slide it carefully up the side of the pot so that my thumb can go underneath the body. With the moth now pinned between two fingers and thumb, I can turn it over and open out the wings on one side with my left hand to inspect the amount of copper (the pictures in the field guide show what you are looking for). This takes a matter of seconds, after which the moth can immediately be released having only lost a few scales (most of which would be lost anyway even if you did use an anaesthetic).
ReplyDeleteIt has long been accepted that markings on the palps are not a safe way to distinguish these two species.
Very helpul tip. I will try that on my next CU agg.
ReplyDeleteThanks all.
ReplyDelete