In that year a total of 22 was released between 2/4 and 25/4.
2019: 30 between 27/2 and 8/4.
2020: 39 between 10/3 and 8/4.
Why they choose to spend the winter in my garage and what their origin is I know not. The larvae feed on various willowherb sp. of which there is none in my garden.
For further details see my note in Nocturnal Record No. 12 (Summer 2020).