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"Small
but perfectly formed": Some
lesser-known westcountry river flies
This page
explores some of the lesser-known species of insects which can be found
if you examine the stones in the
rivers of Dartmoor and South Devon.
Mention caddis and most anglers assume you are
talking about one of the numerous species of relatively large insects
that form a protective case around their bodies from small stones, sand
or pieces of vegetation.
But we also have a much smaller species of caddis - Glossosoma
In addition our rivers contain species of caddis that do not construct
a protective case around their bodies (Rhyacophila
and Hydropsyche),
and - as any Summer visitor will confirm - clouds of biting midges
(Simulium)
which
are eagerly consumed by trout as they struggle to break through the
water surface.
It
is easy to underestimate the difficulty insects experience breaking
through the barrier between water and air, and consequently how exposed
they are to being picked off by hungry trout. Gary LaFontaine points
out that - in human terms - it is equivalent to breaking through three
feet of soil above our heads! |
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Glossosoma
caddis
(popular name: saddle case caddis, igloo caddis,
turtle case caddis, little black short-horned caddis)
Often writers of angling books overlook small flies such as midges and
small caddis in
favour of the larger and more glamorous flies. As Gary
LaFontaine
wrote, "A sad fact of
modern fly-fishing is that so much of the lore is geared to one insect,
mayflies.."
The rivers running off Dartmoor are home to large
numbers of the
inconspicuous Glossosoma caddis which - as this picture shows
- are easy to overlook especially when seen alongside a larger mayfly
nymph.
Glossosoma are small (3-7 mm, hook size 18-22) caddis often present in
large numbers on the algae covered upper (illuminated) surface of
stones in fast
flowing sections
of local rivers. They are thought to be the oldest (i.e. most primitive
in evolutionary terms) type of case-making caddis. The more familiar
caddis which make
tubular cases from sand, stones or vegetaion are thought to be a later
evolutionary development.
Glossosoma larvae have to abandon their cases - rather than add extra
material -
when they outgrow them. At this point they may drift, or be
swept, downstream which
would make them susceptible to predation by trout.
Adult Glossosoma females swim underwater to deposit their eggs. This
may explain the effectiveness of 'wings' on some wet
flies. |
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- Large numbers can be present on top of rocks
- case is a small oval barnacle-like collection of
small
bits of stone
- glossosoma larvae cannot enlarge their case, instead
they abandon their home when they have outgrown it,
and drift downstream = potential trout food
- larvae and pupae have pale creamy tan bodies with
dark brown heads
- adult females dive underwater to lay eggs on rocks
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glossosoma - top view |

glossosoma - bottom view showing head of larva on right |
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- imitate glossosoma pupa with a Sparkle Pupa
- imitate uncased glossosoma larva with a tan Caddis
larva
- imitate egg-laying female with a Diving Caddis using
wet
fly swing, 'Leisenring lift', or 'induced-take techniques with weighted
leader
- adults are small and grey-black in colour

Diving Caddis (Gary LaFontaine)
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Sparkle Pupa (Gary LaFontaine) |

Tan Caddis larva |
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Free-living
caddis: Rhyacophila
(popular name:Sandfly), and Hydropsyche
(net-spinning caddis)
- free-living or caseless caddis; the larvae does not
construct a case
- Rhyacophilia are green colour
- relatively large - 9-15mm in size
- 'Czech nymph' method of fishing mimics behaviour and
location of these insects
- Czech nymphing is a short-line deep-water technique
which
involves 'flicking' rather than casting a very short line upstream and
allowing the flies to dead drift downstream. This process can be
combined with an 'induced take' by lifting the rod.
- the heavy caseless caddis fly can be combined with a
dry
fly which acts as an 'indicator' when a fish takes the caddis- the 'New
Zealand dropper' set-up.
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Rhyacophilia (caseless caddis) larvae |

Hydropsyche larvae |
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Hans van Klinken's caseless caddis
Sawyer's Killer Bug |
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Simulium
(popular
names: biting midges, black gnat, smuts)
- club-shaped larvae found attached by a sucker to
stones, prominent mouth 'brushes'
- pupa floats to surface in a bubble of air
- midge pupae are important trout food
- responsible for 'smutting rise'
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Simulium larvae
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midge pupa

Martin Joergensen's Black Funnel |
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Online
resources
- Rick Hafele's article on Glossosoma
caddis
- Jeff Morgan's article on Glossosoma caddis
- Jeff Morgan's tying of the uncased Glossosoma
larva
- Allen McGee's article on egg-laying caddis
- Westfly article on saddle case caddis
- Martin Joergensen's article on his Black Funnel
- Rick Hafele's article on emergence behaviours
- Rick Hafele's article on micro-caddis
- Pictures of caseless caddis
(Rhyacophilia) larvae
- Hans van Klinken's tying and fishing the caseless
caddis
- Frank Sawyer's Killer Bug
- Czech nymphs
- William H.
Amos, article 'In Praise of Blackflies'
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| anabolia
nervosa: this caddis attaches bits of stick to its case |
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"The great charm of
fly-fishing is
that we are always
learning." - Theodore Gordon |