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Adult Caddisfly and Caddisfly Larva (casemaker) - Order
Trichoptera
Some species of caddisfly larvae use their own glue
to assemble sand grains, bits of shell and even plant fragments into
a tube in which they will hide.
As the larva progresses through five stages (instars), it molts and
builds new larger cases.
Live adult caddisflies photographed in the wild at Winfield, Illinois, USA. |
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Adult caddisfly holds its wings roof-like over its body at rest. |
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Caddisfly adults resemble moths, but the wings are covered with fine hair
istead of scales. (Trichoptera means "hair wing.") Caddisfly larvae are
a favorite food of many fish, including trout, and are used as bait by
fishermen. The larvae are especially sensitive to water pollution and
their numbers can be monitored over a period of time as a good indicator
of water quality. These primitive flying insects are most abundant near
well-aerated streams and fast-flowing water, but also frequent lakes,
ponds and marshes. This specimen was found at the west branch of the
DuPage River, a fairly sluggish body of water, home to both large and
smallmouth bass, walleye, and panfish such as bluegills and sunfish. |
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Adult caddisflies are commonly called sedges. Caddisflies (and mayflies)
frquently hatch en masse, providing swarms of flying insects that
attract sport fish, especially trout. Fishermen take advantage of these
hatches by fly-casting both wet and dry flies mimicking these insects. |
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Photo: Government of New South Wales, Australia
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Caddisflies undergo complete (holometabolous) development. After hatching from
an egg, the lava will progress through five instars (building a new, larger case
at each stage), then pupate inside the last case before emerging as a winged
adult. The larva has six legs arranged in three pairs near the head, and small
hooks near the tail which it uses to anchor itself inside the case. Most species
have gills and get their oxygen from the water that circulates through the case;
this may explain their sensitivity to water pollution which affects the level of
dissolved oxygen in their environment. All development before the adult stage
takes place in water; some species' larvae are predatory and spin silken
structures underwater to trap prey. The predatory species are free-swimming and
do not build cases. |
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Caddisfly larva with case made from plant stems
Photo: Government of New South Wales, Australia
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Case construction is distinctive for each family or genus of caddisfly.
The case is portable, dragged around like a snail shell as the larva moves, and
held in place by a pair of hooked prolegs at the tip of the abdomen. |
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