Early stages of Xylomyidae (wood-soldierflies)

Two species are found in the UK: Solva marginata (Drab Wood-soldierfly) and Xylomya maculata (Wasp Wood-soldierfly). (A third species, Solva varia, was reported based on 19th century specimens but it is not known if these are genuinely British.)

The larvae are found under bark or in decaying wood, and are believed to feed on rotting organic matter. They can be found in the winter, and have been reared by keeping them and some of their substrate in containers that retain moisture but also provide ventilation. The pupa emerges through the skin iof the puparium (the final larval skin, inside which the larva pupates), and the pupa is characteristically left attached to the puparium following the emergence of the adult fly.

Solva marginata (Drab Wood-soldierfly)

Most often found under bark of Poplars, especially Black Poplar, but can be found on other trees as well. Take care when examining bark not to damage the habitat - lifting a few small, loose pieces is often sufficient, and they should be replaced after being examined.

The video and photos below are of larvae from Askett, Buckinghamshire, found on 28 January 2021 (Martin Harvey).



Larva on bark Head of larva
'Tail' of larva Fallen limb of Black Poplar
Fallen limbs of Black Poplar by field edge ditch  


The photo below, by Nigel Jones, shows how the pupal case is left behind after the adult fly has emerged, and is characteristically wedged in to the puparium (final skin of the larva). The larva was found under bark of Sycamore, in Shropshire.


Pupa and pupal case of Solva marginata