Since my last blog post it’s starting to feel that spring has finally arrived! Hopefully this means that from now on there will be a few more moths flying. Over the last few weeks, while awaiting the warmer days, I’ve been continuing to look out for feeding signs and larva.
A great way to search for micro-moths is to keep an eye out for the caterpillar’s preferred food plants and then check for holes and mines they have made in the leaves or stems. Some of these are very distinctive and can even be enough on their own to identify which species made them. One example of this is the tiny holes left in the stems of Cocksfoot grass (Dactylis glomerata) by Glyphipterix simpliciella. After feeding on the flowers of the grass over summer the caterpillar burrows its way inside the hollow stems to sit out the winter within a little paper cocoon, it then pupates inside ready to emerge as an adult moth in late spring.
Another easy sign to spot are the feeding mines made by Stigmella aurella on the leaves of brambles. Although there are lots of species of insect that feed on brambles, these clear white mines are unmistakable*. Once the larva is fully fed it will vacate the mine and spin a cocoon in the vegetation litter below. These tiny moths have several generations in a year and the mines can be spotted at almost any time.
*(well, almost- it should be noted that there is a species called Stigmella auromarginella which makes similar mines on brambles, but this is currently limited to a few sites in Dorset and the Burren in Ireland).
Broom (Cytisus immundella) is a great plant to check for micro caterpillars as there are several species that feed on this. One of these is the bright yellow larva of Trifurcula immundella. To find these look out for greyish-brown lines running the length of the green stems. If you look really closely with a hand lens you might even spot the tiny silvery-grey egg at the start of the mine which will help to confirm that you’re looking at T. immundella and not Leucoptera spartifoliella, which produces a very similar mine but the egg falls off the stem soon after hatching and these yellow caterpillars have a line of brown marks along their length. Or if you find a grey mine on Broom which is quite short it may belong to Phyllonorycter scopariella.
Checking the undersides of the fresh new spring leaves of Oxeye Daisy (Leucanthemum vulgare) will often reward you with the pale caterpillars of Bucculatrix nigricomella. This species starts off by feeding by mining within the leaves then, as it gets larger, it switches to surface feeding. Each time it grows too big and needs to shed its skin, it curls up into a little white silk ‘cocoonet’ before it finally creates a long silken cocoon to pupate in.
As well as looking for larva, last week saw my first trip to Wester Moss with the moth traps. There were no micro species flying sadly but we did catch a few macros, including this lovely Scarce Prominent Odontosia plumigera, which hadn’t been recorded on the site for the last few years.
I’ll be continuing to search in foliage for signs of caterpillar activity, but with the warmer weather and longer days come much more chance to see moths on the wing so hopefully I’ll have a few adults to share very soon! Watch this space, or you can catch me on Twitter too: @catofthewoods.
Thanks to TCV and Esmee Fairburn Foundation for this fantastic opportunity and thanks to Butterfly Conservation for having me!