Description:
This is a member of the Laboulbeniales, a group of insect parasites that do little damage to their host. They lack mycelium and the entire thallus (body) is derived from enlargement and subsequent cell divisions of the two-celled ascospore. The thallus is of determinate growth (i.e. the number and position of the limited number of cells in a species is constant and two individuals will resemble one another far more than in the often confusing array of toadstools and brackets); they may also have plume-like structures (such as here) and triggers that help in ascospore release when an arthropod comes into contact with a mature thallus.
Habitat:
Beetles of the rove beetle genus Philonthus,
Spores:
The spores of Laboulbeniales are generally rather similar and of little taxonomic value. They are usually elongated spindle -shaped with a septum towards one end, at the other end is often a small blob of adhesive material which helps the spore attach itself to an arthropod brushing against the host individual (often during mating) - this blob can just be made out on the extreme right-hand spore issuing from the perithecium.
Additional Notes:
Found on a specimen of the staphylinid beetle Philonthus varians, near Fairburn Ings, West Yorkshire in 1993..
The Laboulbeniales form a highly specialised group - initially not even recognised as fungi - of tiny species which live on living insects, mostly beetles or flies, generally causing their hosts little damage. Few naturalists are aware of their existence, and far fewer study them. Meredith Blackwell's website is a good place to start.
