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Moths: Variety and lack of it

Posted: Monday 29th July 2019 by Twheatear

Three very different common rustics

Coping with moth-y puzzles...

Since we started using a light trap to find the moths in our garden, I've been pleasantly surprised how distinctive most of them are. With a few notable exceptions (pugs!), most are relatively easy to distinguish: at least no harder than little brown birds. And moths have the big advantage that they will sit still in a clear pot until you’re happy with your identification.

Most, because there are a few species that come in a remarkably wide range of colours, and still catch me out. At first sight the three above look very different. And the presence of three forms (my field guide actually illustrates six) means we aren't looking at a simple male/female colour difference. But in fact, they are probably all the same species: the common rustic. For these, and a few others, you need to concentrate on shape and pattern, rather than the colours that fill in the pattern.

And then there's another twist, because it has recently been concluded that there are actually two separate species – common rustic and lesser common rustic – that each have pretty much the same range of colour patterns and sizes. They can only be distinguished under a microscope, and I don't want to kill mine to check. So two moths that look different could actually be the same, but two that look the same could be different. Fortunately moth recorders have a simple solution to these visual puzzles – these all get recorded as "common rustic aggregate".

[With thanks to those who have helped me identify yet another form of common rustic...]

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