| Uniramia |
| --Centipedes |
| --Hexapoda 1 (insects) |
| --Hexapoda 2 (insects) |
| --Hexapoda 3 (insects) |
| --Identification to order level |
| --Insect orders |
| ----Lepidoptera (butterflies, moths) |
| ----Ephemeroptera (mayflies) |
| ----Hemiptera (bugs, cicadas) |
| ----Hymenoptera (bees, ants, wasps & saw flies) |
| ------Bumblebees |
| ----Coleoptera (beetles) |
| ----Dictyoptera (mantids, cockroaches) |
| ----Diptera (true flies) |
| ----Neuroptera (lacewings, ant lions) |
| ----Orthoptera (crickets, locusts) |
| ----Thysanura (bristletails, silver fish) |
| ----Strepsiptera (stylops) |
| ----Thysanoptera (thrips) |
| ----Odonata (dragonflies, damselflies) |
| ----Trichoptera (caddis flies) |
| ----Siphonaptera (fleas) |
| ----Isoptera (termites) |
| ----Phasmida (stick & leaf insects) |
| ----Dermaptera (earwigs) |
| ----Anoplura/siphunculata (sucking lice) |
| ----Mallophaga (biting lice, bird lice) |
| ----Psocoptera (book, bark, dust lice) |
| ----Mecoptera (scorpion flies) |
| ----Collembola (springtail) |
| ----Embioptera (web spinners) |
| ----Plecoptera (stone flies) |
| ----Diplura (bristletails) |
| ----Protura |
| ----Zoraptera |
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Trichoptera fast facts |
8 000 species worldwide, 400 in Europe, over 230 in Northern Europe, and about 200 in Britain.
Both adults and larvae are important food source of certain fish and birds.
Trichos (Greek) = hair, pteron (Gk.) = wings.
Adults. Usually found over or near freshwater.
2 pairs hairy wings.
Usually the rear wing is broader than the fore wing.
At rest the wings are held roof-wise over the body.
Mouthparts greatly reduced.
Legs long with spurs at tip of tibia (see drawing below).
Prominent, but small compound eyes and 3 ocelli.
Long antennae, bristle-like and many segmented.
Dull brown or grey.
Weak fliers, and fly mainly in late afternoon or night.
Larvae.
Caterpillar-like with six legs.
Usually inside an open-ended cylindrical case.
Biting mouthparts.
Aquatic in clean freshwater.
Eggs
Eggs laid underwater on plant stem in a gelatinous mass. |
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Eggs
The eggs usually hatch around two weeks after they have been laid. If the water has dried up in a seasonal pond or stream the eggs can lie |
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| dormant for a few months. The eggs are covered with mucilage which swells upon contact with water. To the naked eye the eggs look like miniature frog spawn, but the egg of Phryganea atrata above shows their microstructure. |
The case.
Many caddis fly larvae make an open-ended cylindrical case to surround their bodies. The cases are made from various materials (see below left and right), and some species can be identified from their case alone. As the larva grows the case is added to at the front end and pieces may be discarded from the rear end. This is why the front opening is wider. Although the case is large enough to hold the entire body usually the head and the three thoracic segments with the legs are outside the case.
The material used to make the case is held together by silken threads that come from a spinneret near the mouth. A current of water is continually passing through the case to come in contact with the gills on the abdomen. |
If the larva feels threatened it can retreat into the case. It has two appendages at the rear of its abdomen which hold on to the silken lining of the case and can pull itself inside. Some species move around carrying their case, and others fix the case to the underside of a stone or other suitable material. Larva living in fast-flowing water may add a larger stone or pebble to the case to stop themselves being swept away as can be seen below right where the case has one relatively large stone fixed to a case made of grains of sand. On the right are cases made of shells. The larvae choose both occupied and unoccupied shells. Below right is a case made of leaves, and above that one made of reed fragments. There are a few species which do not make a case and these usually have a tougher exoskeleton. Some of these construct nets between vegetation, the nets are used to trap food particles. Others are completely free-living.
Larva The larva are omnivorous. The movement of the larva inside the case helps to draw a steady current of water past the gills enabling a constant supply of oxygen. They pupate inside the case while they are still underwater. Just before they pupate they close off both ends of the cases with a grid of silken threads. This gives them protection while still allowing a current of water to reach their gills. The free-living larvae attach themselves to some suitable substrate with a silken net before pupation. Just before emerging as an adult the pupa breaks out of the case or web and crawls to the surface. Some crawl up plant stems or stones to emerge as adults, others break out of the pupal skin on the water surface. These use the old skin as a raft to rest on until their wings harden enough to fly.
Adults
Their flight is heavy and awkward, and they fly mainly at dusk. During the day they hide in waterside vegetation. Some adults feed on nectar or pollen, but many do not feed at all. A few species have wingless females. The number spurs on each tibia are important characteristics used in identification (see Phryganea grandis below). Mating takes place while resting on vegetation, although in some instances mating may start on the wing. The life cycle usually takes one year. |
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Leptoceridae family. The females in this family lay eggs in a jelly mass on stones and plants. The larval cases (see Trianodes sp. left) are relatively narrow and some are slightly curved. They tend to be made of plant material or sand grains. Most of the larvae are vegetarian.
On the left is Trianodes sp., its case is similar to those in the Phryganidae family (see above). It is 20 30 mm long, and made of plant material arranged in a spiral. The larva is an active swimmer, and its 3rd. pair of legs are very long and covered in hairs. Before it pupates the larva fixes the case to a plant. The eggs are found on the undersides of floating leaves.
Larvae in the genus Leptocercus have a curved case usually made of sand grains and 11 - 17 mm long. On the left is an adult in resting position. |
Rhyacophilidae family. The eggs are stuck to the bottom of stones in streams. The larvae (right) are carnivorous and found in rapidly-flowing water. Not all species in this family construct cases, and the ones of those who do tend to be rather simple and crude.
Rhyacophila sp. larvae (right) are found on the under surface of stones and fast-flowing water. They do no build a case. Fully grown larvae are 9 - 14 mm long and are green and brown. They move around quite quickly using their legs and anal appendages to hold on to stones to avoid being swept away. The larvae pupate in the late autumn in a shelter they make of small stones stuck to the underside of a larger stone. Inside this is makes a cocoon. |
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| The Hydropsychidae family larvae and eggs are found in fast-flowing streams. The eggs are cemented to the underside of stones. The larvae (see Hydropsyche sp. right), are very active, and when fully grown can be 10 - 20 mm long. Very young larvae do not have gills. Note that the anal appendages are large. They do not build a case, but live in a silk net stuck to the underside of a stone. Inside the net there is a silk tunnel, open at the end which faces the flow of water, and closed at the other end. The larva lives in the tunnel and eats anything - animal or vegetable - that is caught in the net. Before pupating the larva constructs a shelter made of small stones. |
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Polycentropidae family. The larvae, (see Polycentropus sp. on the left) are carnivorous web spinners with no abdominal gills, but 5 anal gills. They have large anal appendages with terminal hooks. They live inside a silk web and do not construct a case.
On the left is Polycentropus sp. a fully grown larva is about 12 mm long. They are found in rivers and lake edges, and are sometimes found in groups. |
The Philopotamidae family. The larvae have orange or yellow-brown, narrow heads. On the right is Philopotamus sp.
Limnephilidae family. The larvae make their cases out of a variety of materials. They are found in stagnant or slow- moving water. Quite often the case is so heavy that the larva cannot swim, but only crawls around. |
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Odontoceridae. On the left is Odontocerum albicorne. It makes its nest out of grains of sand. |
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The Canny Scot |
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