This order of insects are commonly named caddisflies. They are found underwater in cases and often attached to rocks. Trichoptera are most known for their unique characteristic among aquatic insects to spin silk. This silk is used to build shelter, food-collecting nets, and is used to help anchor the insect to the substrate. Most Trichoptera live in and build a case with the exception of Rhyacophilidae, which are free-living, and Hydropsychidae and Philopotamidae, which build nets. Rhyacophilidae are most abundant in lotic, or fast current aquatic habitats. Hydropsychidae and Philopotamidae catch their food as swift currents bring particles of plant material along with the water flow to their nets.
Family Brachycentridae
Humpless Case-Maker Caddisfly
Brachycentrid larvae are most frequently found in lotic water systems. They are usually attached to hard surfaces or floating in aquatic moss. These larvae build cases from strips of material that are attached to form a four sided or rounded case. From resting inside the case, Brachcentrid larvae use their middle and hind legs to filter food from the water and substrate in front of them. Larvae are medium in size. The larval body length is 8 to 13 mm. The antennae are held close to the body and there is either one gill present, or there are no gills at all.
Family Glossosmatidae
Saddle Case-Maker Caddisflies
These caddisflies are commonly found on top of rocks in streams. These caddisflies scrape algae and diatoms off of rocks from the safety of their cases which help protect them from predators. Glossosmatid larvae are most commonly found in cool and clear lotic water systems, but they have also been documented in large rivers and lake edges where the current is fast enough and appropriate substrate is present.
Family Helicopsychidae
Snail Case-Maker Caddisflies
As their common name, snail case-maker, suggests, these caddisflies create cases that resemble the shell of a snail. The twisted shape of the case provides structural integrity and is more difficult to crush, thus protecting the larvae that live inside somewhat more effectively, than most other caddisfly cases. Helicopsychid larvae are most frequently found in streams with sandy substrate. The larva is most often within its case attached to stones or other solid substrate. The larval body length is about 8 mm, and the body is rounded to fit into the snail-like case. Branched gills are present on the first few abdominal segments.
Family Hydropsychidae
Common Net-spinner caddisflies
Hydropsychid larvae have a unique way to collect food. The larva spins a silk net in which it resides. The larva is able to collect detritus and other food sources which collect on the net. Hydropsychid caddisflies will defend their nets, or retreats if threatened. These caddisflies are the most commonly collected from areas where there is a cobblestone substrate. They are also found in areas where there is a solid woody substrate that they can attach their nets to. The larval body length is 9 to 30 mm. Most of the abdominal segments have tufts of gills, and there are many setae, or hairs on the final abdominal segment.
Family Hydroptilidae
Micro Caddisflies
As their common name, micro caddisflies, implies, Hydroptilidae are small in size compared to other caddisflies. The average larval body length is between 2 and 6 mm.
Hydroptilidae under go a unique larval development. In the first four instars, or stages of the larval life cycle, larvae are small and free-swimming. It is not until these larvae molt into their fifth instar that they begin to build cases. These cases may be built from sand, algae, or detritus. The larval body lacks gills on abdominal segments.
Family Lepidostomatidae
Lepidostomatid Case-maker caddisflies
These caddisfly larvae are most frequent in cool slow moving waters where detritus, or dead organic matter, collects. Lepidostomatid larvae use the accumulated plant matter, including twigs, pieces of bark, and leaves to build four-sided cases. The larval body is medium in size compared to other caddisfly larvae; the body length is between 7 and 13 mm. There is either a single gill, or no gills present. The body has lateral humps on abdominal segment 1.
Family Leptoceridae
Long-horned Case-maker caddisflies
Both the habitat and case-making behavior of Leptoceridae are variable. These larvae may be found in all freshwater aquatic systems, but they are most common in standing water of ponds and marshes. They build cases from rock, sand, leaves, twigs, or freshwater sponges; the shapes and sizes of these cases are variable between species. In addition some species are free-swimming and are able to leave the protection of their case when needed. The larval body is relatively small; the average body length is between 7 to 15 mm. The presence and location of gills is variable among species. The antennae are long and pronounced, inspiring the family’s common name, long-horned caddisflies.
Family Limnephilidae
Northern case maker caddisflies
These larvae are most frequently found on vegetation or attached to rocks in many rivers, lakes, and streams. The larva’s local habitat determines what type of material the larvae will use in construction of its case. In lentic environments, the larvae tends to create it case from plant material and detritus, while in lotic environments the larvae builds its case out of minerals and pebbles commonly found in the substrate. The larval body size is medium to large; the average length is between 8 and 35 mm. Limnephilid larvae have antennae that attach to the head between the mandible and the eye. The presence and location of gills is variable, and there are humps present on abdominal segment 1.
Family Molannidae
Hood Case-maker caddisflies
Molannid larvae create cases from sand that have a hood that stretches over the opening of the case allowing the larvae to be protected while moving about in the case. These larvae are commonly found in lakes and in more slowly moving streams and rivers. The larval body size is medium compared to other caddisfly larvae; the average body length is 19 mm. There is a tarsal claw on the hind leg that is covered with setae, or small hairs. There are abdominal gills present. The gills are either simple or branched.
Family Odontoceridae
Strong Case-maker caddisflies
As their common name suggest, the cases that odonotocerid larvae create are extremely strong. The cases are made out of sand and stone particles and are especially strong to withstand frequent burrowing. These larvae are most often found in moving water where there are deposits of gravel and sand, the substrate used to create their cases. The larvae are medium in size, and the average body length is between 9 and 10 mm. These larvae possess antennae that are located near the mandible. There are dorsal and lateral humps on abdominal segment 1.
Family Philipotamidae
Finger-Net Caddisflies
Philipotamid larvae build long and slender tube shaped nets out of silk that are used to filter small floating particles. The fungus and bacteria that grows on these particles is then scraped from the net and ingested. These larvae are most frequently found in lotic water systems under rocks and logs. The larval body size is medium, and the average larva body length is 13 to 17 mm. The head has brown or orange coloration, and there are abdominal gills present.
Family Phryganeidae
Giant Case-maker caddisflies
Phryganeid larvae are very large when fully developed. The average larval body length is 20 to 45 mm in length. These larvae are most frequently found at the edge of ponds and in lakes and streams in places of slow current. They are usually near submerged aquatic vegetation and in overhanging vegetation along the shore line. The larvae use these plant materials to build cases which they abandon (unlike other caddisflies) when they are threatened or the case is disturbed. There are stripes on the head, and lateral humps on the first abdominal segment.
Family Polycentropodidae
Tube-making and Trumpet-net caddisflies
These caddisflies are most frequently found the slow moving streams and rivers, or in lakes and ponds. Polycentropodid larvae feed by either filtering small invertebrates from the water or attacking prey that ventures near the opening of their case. Some species attach silk threads from their case to surrounding substrate as a way to detect the presence of near-by prey by sensing the vibrations in the string. The larval body length is between 8 and 25 mm, and there are abdominal gills are absent.
Family Psychomyiidae
Tube-making and Trumpet-net caddisflies
These caddisflies live in cool lotic aquatic environments and are often found attached to rocks and submerged logs. The larval body size is medium. The average length is 10 to 15 mm. Abdominal gills are absent. These caddisflies build silk tubes, but they do not use them to filter particles from the water. Instead these collectors and gatherers feed on the detritus that passes directly in front of the opening to their case, or that which occur on the near by substrate.
Family Rhyacophilidae
Free-living Caddisflies
Rhyacophilidae is the only family of caddisflies where the larvae do not build a case or a net. Instead, Rhycophilid larvae move along the substrate looking for prey. While searching for prey, usually consisting of other small invertebrates, the larvae attached themselves with a string of silk to the substrate to prevent being swept away by the current. These larvae are most frequently found in lotic environments under rocks or in accumulated algae. The larval body size is between 12 and 32 mm in length. There are long anal prolegs on the final abdominal segment, and the presence of gills is variable. Rhyacophild larvae do create a case when they are fully developed as a larvae to protect themselves during pupation.
Family Sericostomatidae
Sericostomatid case-maker caddisflies
Sericostomatid larvae are found in small streams and at the edges of lakes where there are deposits of sand, the substrate used to create their cases. These larvae are not easily collected because they frequently burrow in the sand making them difficult to see. The larval body length may be up to 19 mm in length. The hind legs are longer than the middle legs, and abdominal gills are either single or branched. There is a conspicuous proleg on the final abdominal segment that is covered in setae or hairs.
Family Uenoidae
Uenoid Case-maker caddisflies
These caddisfly larvae are most commonly found in small streams where there is a fast current. They are usually attached to rocks and stones where the larvae scrape diatoms and small organic particles from the rocks where they are attached. There are lateral humps located on abdominal segment 1, and antennae are located between the eye and the mandible.
Trichoptera Life History
Larvae and Pupae
In general, larvae develop through 5 to 8 instars within a one year period, but some species require 2 years to develop. When larval development is complete, the insect will attach its case to the substrate and seal off the ends. While sealed inside the case, the pupal stage lasts from 2 to 3 weeks.
Adult
When the pupa development is complete, the new adult will emerge from the case and swim to the water’s surface. The adult life stage is short; most Trichopteran adults live for less than one month. Adults are primarily active at night. The female will deposit eggs onto the surface of the water in most families, but in some families eggs are laid in dry basins during drought seasons and the eggs will not hatch until water returns.
Feeding Habits
Larval food collection is extremely diverse between genera. Some larvae are mainly predaceous, while others eat only plant materials, including diatoms and algae. Many species use their ability to spin silk to create a food capturing device. Adults from some species feed on plant nectar.
Ecological Importance
Trichoptera are important to aquatic ecosystems because they filter and process organic materials, and they are an important food source in the diet of freshwater fish. These species are also sensitive to pollution, so fluctuations in Tripcoptera populations may reflect changes in local water quality and ecosystem health.
