Making a start on the Lepidoptera

Making a start on the Lepidoptera

Having shunned the lepidoptera for the last few decades, I've decided to have a go at moth identification from a standing start. To start with it would be to look at what turns up attracted to light indoors at home.

It quickly became apparent that working from a standard key was not a good idea. Very early on the published keys to family use characters of the wing veins which are completely covered with scales in most moths. So armed with my copy of Sterling & Parsons, Field Guide to the Micro Moths of Great Britain and Ireland I start doing what I guess most people do – trawl through the illustrations and make a short-list of what it could be and then read the text to eliminate any species it can't be. What could be easier?

So the first moth to appear was a reasonably large one with its front wings 15 mm. The labial palps were directed straight forward, so the head looked as if it was extended as a snout. 

A look through the "at a glance guide" seemed to suggest Pyralidae or Crambidae. So onwards to the colour plates and then the problem with picture comparison comes – a single picture doesn't take variation, wings sitting differently, angle of lighting and light intensity into account. Next make a list of all the species marked common in the text assuming that anything that turns up in a suburban garden in north Hampshire isn't likely to be rare. Then back to looking at a subset of the pictures and it seems that Aphomia sociella matches best. My specimen shows definite greenish and pinkish shades, which are not shown in the illustration. Onto image searching on the internet and now you see the variation and behold one image looks very much like my moth.  The big difference is that the wings are rolled around the abdomen rather than held flatter as in the illustration. 

Then for fun, I thought I'd have a look at the wing venation. Remove front and hind wing from the right side of the moth. Place a drop of propanol on a microscope slide and then place the wing in the alcohol. Using a soft hair paint brush very gently stroke the wing surface towards the tip. Off come the scales (the process is called denuding the wing) with many of them sticking to the brush so wipe on tissue and add more alcohol. Once one side of the wing looks clear, turn the wing over in more alcohol and repeat the process. Now the veins become clear and it's a matter of interpreting them.

Again problems arise. Searching online shows that there have been two numbering systems for moth wings. One appears to be specific to lepidoptera – numbering the veins from 1-12 on the front wing, starting from the back of the wing. The second is based on the Comstock-Needham system, dividing the wing into different areas – costa, subcosta, radial, medial, cubital and anal. This I'm familiar with and it is the system used in recent publications. Most of the veins arise from the margin of an elongate area enclosed by veins in the middle of the wing and it seemed rather arbitrary where the dividing line between R veins and M veins except that the accepted maximum number of R veins is 5. The enclosed area is variously called the discal cell, discoidal cell or simply “the cell”.