Peatland wildlife
Insect larvae
A wide range of insects have an aquatic phase and can be found
in peatland pools. Some of the most common aquatic insect larvae
include:
| Dragonfly larvae |
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Dragonfly and Damselfly nymphs
The juvenile stage of both dragonflies and damselflies are
known as nymphs rather than larvae. Unlike larvae, nymphs resemble
the adult apart from underdeveloped wings and develop into adults
without a pupa phase. Females lay their eggs in ponds and pools
during the summer months. Eggs laid early in the year will hatch
into nymphs that summer, while those laid late in the year will
hatch in the next year.
Damselfly and, more particularly, dragonfly nymphs are fierce
predators – dragonfly nymphs of up to 55mm long are capable
of taking small fish and tadpoles using specially adapted hinged
jaws. They can crawl over vegetation or swim through the water
in a surging motion. Damselfly nymphs are smaller but also feed
on a wide range of aquatic invertebrates.
The nymph phase can last from 1 to 5 years depending on the
species but they are often difficult to see because they are
well camouflaged. For both dragonflies or damselflies, the transformation
from an aquatic nymph to flying adult requires major changes
within the body. The adult body begins to develop within the
nymph before it moves out of the water. When the nymph is ready
to transform into an adult, it crawls up the stem of a plant
until it is out of the water, its skin splits and the adult
dragonfly emerges. This process normally happens before dawn
as the newly emerged adult cannot fly until its wings are fully
expanded and its body has reached a certain temperature.
| Caddis fly larvae |
 |
Caddis fly larvae
Caddis fly larvae are common aquatic larvae but are well camouflaged
so are often difficult to see. Some are free-living but many
live in cases constructed from a variety of materials such as
twigs, leaves, sand grains and small stones held together by
silk. They generally crawl around on the bottom sediment but
some can swim.
Most caddis fly larvae are omnivorous but some are carnivores
and will eat smaller larvae. They themselves provide an abundant
food supply for invertebrates, amphibians and fish.
Pupation takes place in a cocoon which is spun inside the case.
The nymph seals and anchors the case to something firm. In some
species the adults hatch at the surface, in others they crawl
up vegetation to reach the surface. The adults live among vegetation
and fly mainly at dusk, laying their eggs in water or on plants
overhanging ponds, streams and ditches.
| Mayfly larvae |
 |
Mayfly nymphs
While there are many species of mayfly, all are characterised
by three long tails, a long larval stage and the distinctive,
vertically held wings of the resting adult. The three tails
makes the mayfly nymph easy to differentiate from stonefly larva
which have only two tails.
Despite their name, adult mayflies can be found throughout
the warmer seasons while the larvae are found all year round
in peatland pools. Depending on the species, a mayfly nymph
will take between two months and two years to develop, moulting
up to 27 times throughout this time. The larvae feed on algae
during their development but the adults do not feed at all during
their short life. Mayflies are sensitive to pollution and as
water quality decreases so too does the diversity of mayflies
present.
Once emerged the winged adults only live for a few days at
most with the sole purpose of mating and laying eggs. Large
swarms of mating mayflies and caddis flies often occur when
all the nymphs of a single species emerge at the same time.
When the females have mated, they fly upstream and drop their
eggs onto the water or dive into the stream to attach them to
rocks or leaves.
Bloodworms
(Non-biting midge larva)
Chironomus annularis |
 |
Bloodworms (Non-biting midge larva)
Chironomus annularis
It is difficult to differentiate adult non-biting midges from
their biting relations, and both types can be found in large
numbers swarming above water just before dark. Egg-laying females
drop large egg masses in water. The larvae live in water, have
a variety of colours and can occur in huge numbers. The bright
red colour of bloodworms is due to the presence of a haemoglobin-like
pigment, which helps the larvae to absorb what little oxygen
is available in stagnant water.
The larvae feed on decaying organic matter in the muddy sediments
at the bottom of ponds while they themselves form a major food
source for fish and other invertebrates.
