Caddis Flies
Written by: dave b
One of the most abundant flies in Ontario is the Caddis fly. This fly goes through 3 basic stages in its life: Pupa, Larva and air borne fly. Caddis are very important to the fly fisher because they are a staple in nearly all species of fishes diets.
Caddis Flies of
Ontario
Caddisflies or sedge-flies
(Order Trichoptera, from Greek trich, “hair”, and ptera, “wings”)
Caddis are small moth-like insects that have two pairs wings. They are closely related to Lepidoptera (moths and butterflies) which have scales on their wings, and the two orders together form the superorder Amphiesmenoptera. Caddisflies have aquatic larvae and are found in a wide variety of habitats such as streams, rivers, lakes, ponds, spring seeps, and temporary waters (vernal pools). The larvae of many species make protective cases of silk decorated with gravel, sand, twigs or other debris.
Many species of caddisfly larvae enter a stage of inactivity called
the pupa stage for weeks or months after they mature but prior to
emergence. Their emergence is then triggered by cooling water
temperatures in the fall, effectively synchronizing the adult activity
to make mate-finding easier. In the Northwestern US, caddisfly larvae
within their gravel cases are called ‘periwinkles.’
"Caddis Larvae" (photo – D. Barrett)
"Caddis Larvae" (photo – D. Barrett)
Caddisfly pupation occurs much like pupation of Lepidoptera. That is, caddisflies pupate
in a cocoon spun from silk. Caddisflies which build the portable cases
attach their case to some underwater object, seal the front and back
apertures against predation though still allowing water flow, and
pupate within it. Once fully developed, most pupal caddisflies cut
through their cases with a special pair of mandibles, swim up to the
water surface, cast off skin and the now-obsolete gills and mandibles,
and emerge as fully formed adults. In a minority of species, the pupae
swim to shore (either below the water – see figure – or across the
surface) and crawl out to emerge. Many of them are able to fly
immediately after breaking from their pupal skin.
"Caddis Pupa" (photo – D. Barrett)
The adult stage of caddisflies, in most cases, is very shortlived,
usually only 1-2 weeks, but can sometimes last for 2 months. Most
adults are non-feeding and are equipped mainly to mate. Once mated, the
female caddisfly will often lay eggs (enclosed in a gelatinous mass) by
attaching them above or below the water surface. Eggs hatch in as little as three weeks.
"Caddis Adult" (photo – Bruce Marlin)
Caddisflies in most temperate areas complete their lifecycles
in a single year. The general temperate-zone lifecycle pattern is one
of larval feeding and growth in autumn, winter, and spring, with adult
emergence between late spring and early fall, although the adult
activity of a few species peaks in the winter. Larvae are active in
very cold water and can frequently be observed feeding under ice. In
common with many aquatic insect species, many caddisfly adults emerge
synchronously en masse. Such emergence patterns ensure that
most caddisflies will encounter a member of the opposite gender in a
timely fashion. Mass emergences of this nature are called ‘hatches’ by
salmon and trout anglers, and salmonid fish species will frequently
‘switch’ to whatever species is emerging on a particular day. Anglers
take advantage of this behavior by matching their artificial flies to the appropriate fly.
Sources:
Dave Barrett
Wikipedia
