Double mounting with polyporous fungus blocks

[Charles Bird]

A number of sources advocate double mounting micro moths with polyporous
fungus blocks (eg. Covell, Eastern Moths, p 21). More recently, Landry &
Landry, J. Lep Soc. 48:222 state, "Traditionally, blocks have been cut from
strips of polypore fungi (especially from birch bracket fungus). Normally
it is easy to procure polypore strips from naturalist supply houses, but
periodically they tend to become very difficult to obtain."

I recently tried cutting strips from freshly collected specimens of Fomes
fomentarius [Tinder Conk] from birch and from Phellinus tremulae (Fomes
igniarius) [False Tinder Conk] from trembling aspen but found both to be
too hard. Perhaps these are the wrong species or I should have collected
them at another time of the year. Ideas anyone?

Landry & Landry (p. 223) recommend against using blocks made from balsa,
cork, and polystyrene foam (styrofoam) as they are either too hard or are
not rubbery enough to firmly hold a minuten pin. They further state that
the durability of blocks made from a silicon rubber compound is uncertain.
Schauff, Collecting and Preserving Insects and Mites (p. 32), however,
appears to feel that silicone rubber blocks are OK.

I notice that the latest Bioquip catalog (p. 33) lists only inert silicon
rubber and plastazote double mount strips. Is there still a source of
supply for polyporous fungus blocks?

It would appear from the above that polyporous blocks are the traditional
favorite but that plastazote blocks may be the current favorite. Your views
would be appreciated.

Charley