A lot of the things I've posted recently have been quite local, or at least habitat restricted. This has not been through design, they just happen to be the things I've bumped into. Todays species in contrast, is something that everyone should be able to find.
Coleophora serratella feeds on a range of deciduous trees but is particularly common on birch. Like almost all the species in this genus, the larva inhabits a case from which it makes blotch mines with an entrance hole on the underside of the leaf.
The larva mines as far as it can reach whilst keeping it's 'tail' within the case and then it moves to make a fresh mine, either on the same leaf as shown above or on another leaf nearby.
C. serratella makes two different cases; one in which it overwinters and feeds briefly in the spring, and then a larger case in which it completes its development.
The picture above shows the overwintering case that has been afixed to the base of the leaf. Next to the case is an excised piece of leaf that has been used to make the new case. The spring case is shown below.
Larval feeding signs alone cannot be used to record this species as there are other Colephora species which feed on birch (and other trees). If the case is not on one of the leaves where the feeding signs are, looking at adjacent twigs as it may be fixed to them for pupation.