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”.
