This is another micro moth new to D&G! It was discovered some time ago by Richard Mearns in the unusual habitat of a lichen covered tree stump, shown below, near Ironhirst Loch, Dumfriesshire. Formerly considered a separate species, it is now considered to be a specific form of the Grey Bagworm Luffia lapidella.
In close up a single bagworm can be seen as a lichen/algae covered case attached to the bark.
The photo below shows another bagworm amongst the lichen making it almost impossible to see.
The actual bagworm’s case, three old ones shown below, is tiny (5-7mm fully grown) and is a tilted, swollen cone, circular in cross-section, made out of silk with various fragments of lichens attached to the outside. This case is where the caterpillar lives, head down, feeding on algae and lichen. In this site, despite a lot of searching, Richard did not find any living caterpillars but only a few old cases fixed to the tree.
The Bagworms is a small family of moths (Psychidae) all of which make cases of this sort to protect the larva. There are 18 species in the UK, seven of which have been found in Scotland although only one other has been seen so far in D&G.
In this species the life history is very intriguing. The young caterpillars (fig. D below) start to feed and make themselves a case (fig. C below) and overwinter at this stage. The next year they continue to grow and by June, when fully grown, fix one end of their case to the tree and pupate within their case. The hatching adults emerge in July completely wingless (fig. A below) and all of them female as there are no males in this form! This parthenogenetic moth does not feed or, of course, mate and uses its very long ovipositor to lay unfertilised, thick shelled eggs in the bottom of the vacated case. The young caterpillars hatch out in four to five weeks.
The question is how do these moths without any flying females colonise new tree trunks? Careful studies have shown that the newly emerged caterpillars produce long strands of silk (also used for making their cases) to act as parachutes allowing the wind to blow them to new sites. In some places the caterpillars in their cases occur in huge numbers and in these conditions migration to new tree stumps is essential.
This species is common and widespread in southern England and Wales but further north than Manchester only a couple of records have been made in central Scotland. In Cornwall a form of this species (known as the Grey Bagworm) is found on lichen covered rocks and does produce winged males. The moths have been found on all kinds of trees, rocks and even fence posts densely covered by lichens especially where the single celled green algae Pleurococcus grows in abundance. It follows that this must be a species which is overlooked as such habitats are rarely searched for moths. As the old cases persist for some time it is possible to find this species at any time of year – plenty of opportunities for some very careful searching. There are other similar species which might confuse the identification and good photographs and/or a specimen case will be needed to be certain it is Luffia.
