Fen Management Handbook - Scottish Natural Heritage

The mud snail
Omphiscola glabra
(12–20mm in length),
is restricted to very
specific, and often small
habitat niches. (Dr. Roy
Anderson).
The taxonomic range of interest amongst fenland invertebrates is so large that
the list of associated groups is little more than a checklist of major invertebrate
groups. For example Wicken Fen, in Cambridgeshire, has recorded over 1000
species in each of three groups of insects, the flies (1,893 species), the beetles
(1,527 species) and the moths (1,083 species). In general, emphasis is on those
invertebrate groups with the largest number of species, for example water beetles
and moths as well as highly visible groups, such as butterflies and dragonflies.
The black darter
(Sympetrum danae), a
dragonfly of acidic pools
particularly associated
with poor fen vegetation
and cutover bogs (Dr.
Roy Anderson).
A similar approach to that applied to birds can be adopted when considering the
invertebrate fauna and interest associated with different vegetation structures
and fen habitats. The table below provides a structural classification, albeit an
artificial one, in that it presents, as discrete categories, features and structures that
are in reality part of a continuum. This is a more useful checklist to have in mind
when considering management other than that based on taxonomy, but it must
be emphasised that this mosaic of fen communities is frequently associated with
other semi-natural habitats such as open water and woodland carr, which are often
essential for many invertebrate groups found in fens.
Further guidance on habitat characteristics and features beneficial
to invertebrates can be found in Kirby (1992) and Fry and Lonsdale
(1991). Further information on the groups of invertebrates associated
with fens is also available from www.buglife.org.uk, but bear in mind that
not all groups are included, and there is implied variation in the definition
of fen in the accounts of different groups in this multi-authored work.
The great diving beetle
(Dytiscus marginalis) is one
of many large predatory
water beetlews commonly
found in fens and is easily
observed in pools. They
predate in both their larval
and adult form on smaller
aquatic invertebrates,
tadpoles and small fish
(Dr. Roy Anderson).
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