Caddisfly Facts: Their Larvae Live in the Case Made of Rocks, Leaves and Twigs

Discover the hidden world of the caddisfly, nature’s master architects. These incredible insects construct intricate protective cases, using silk and materials from their surroundings. From water-dwelling larvae to graceful-winged adults, their transformation is truly mesmerizing. Delve into the mysteries of these tiny creatures and unlock the facts of their remarkable lives.

Phylum: Arthropoda
Class: Insecta
Order: Trichoptera

1. They look like moths

Caddisflies (or caddis flies), alternatively known as rail-flies or sedge flies, are insect species resembling moths. Caddisflies, also referred to as “sedge flies,” are insect species that resemble moths. There is a wide variety of caddisflies, with approximately 14,500 known species. Their typical size ranges from 3 to 15 mm, however, some of the largest caddisflies can reach lengths of over 3cm.

The cinnamon sedge is the most common caddisfly, with approximately 30 different species belonging to this group. The other caddis flies are the long-horned caddisfly (like the black dancer caddis fly), brachycentrus caddis fly, spotted sedge caddis fly, northern caddisfly, or zebra caddisfly. The insects often have dark colors like brown, some can feature bright hues like orange. On the other hand, their larvae are brown, green, or olive.

The caddisfly adult

These insects can be classified into five groups according to the behavior of their larvae: saddle-case caddis, purse-case caddis, tube-case caddis, free-living caddis, and net-spinning caddis. Each group displays unique characteristics in their lifestyle and how they construct their cases.

In terms of appearance, the adults of the species exhibit resemblances to butterflies and moths. They have 3 body parts, 6 legs, and 2 antennae. Nevertheless, they differ from butterflies and moths in lacking the elongated siphoning mouthparts.

When not active, their wings are folded in a tent-like manner along their bodies. Similar to moths, their forewings are covered in hair rather than scales. Their elongated, filamentous antennae are typically the same length as their bodies. These creatures generally sport dull and somber shades, while their hindwings, which are often concealed beneath the forewings, are translucent.

2. They are known for their larvae

Caddisfly larvae are primarily recognized in their larval stages. While identifying individual caddisfly species can pose a challenge, their larvae are comparatively simpler to distinguish thanks to their unique cases.

These larvae reside in aquatic environments and employ silk secreted from glands near their mouths to construct cases. Certain larvae make rounded and humped cases using stones and sands, while others utilize cut fragments of plant material such as leaves and twigs to form lumpy cases.

The majority of larvae that dwell in shelters come in two forms: fixed or transportable. Some carry their larvae shelters when eating, while others stay firmly anchored to a rock. There is a small number of larvae species that are capable of free-living and only construct shelters when they are prepared for pupation.

Caddisfly larvae, while residing underwater, have adapted to an aquatic lifestyle and rely on water as their source of oxygen. The mobile species use their gills to actively transport water and extract oxygen from it. On the other hand, still, species employ a unique undulating motion to facilitate the movement of water over their gills. The presence of larval cases in sedentary caddisflies plays a crucial role in either limiting or guiding the water flow. Removing these cases typically results in the death of the larvae.

3. They eat various food

Due to the abundance of caddisfly species, they exhibit a wide range of diets and feeding strategies. They are omnivore species.

During their larval stage, their feeding strategies can vary depending on the seasonal fluctuations in food availability and larval development. They can graze on algae or eat fallen leaves, plant fragments, and other organic matter. Additionally, certain species adopt a predatory nature, targeting small aquatic invertebrates and other prey in slower-moving waters. These adaptable caddisflies consume both living organisms and decaying matter to sustain themselves.

They make nests to get food

Some find food by using silk to spin intricate nets designed to ensnare food particles from the water, enabling the larvae to feed on the gathered food. They might also display discerning feeding preferences, favoring nutrient-rich foods.

Upon reaching maturity, the insects feed on nectar and other plant fluids to sustain themselves. However, some species do not eat at all due to their underdeveloped mouthparts. That’s why they barely bite humans.

The larvae have a vital function in stream ecosystems as they regulate the population of algae and provide a significant food source for various animals. They’re eaten by Pacific giant salamanders, water shrews, and fish (trout, salmon, sculpins, darters, and eels). Their adults are preyed upon by many predators including dragonflies, frogs, birds, bats, spiders, and lizards.

4. They can be found everywhere

Caddisflies, a commonly found insect species, live in diverse habitats. Similar to stoneflies, dobsonflies, and mayflies, most caddisfly larvae live underwater. However, the Enoicyla pusilla larvae distinguish themselves from other caddisfly species by living among leaf litter in the forests of the West Midlands. People call them the land caddis.

They can be found in temperate ponds, lakes, and streams, such as slow-moving rivers, serene lakes, ephemeral spring seeps, and rapid mountain streams. Typically, they reside beneath rocks and logs within swiftly flowing streams.

The cased caddis fly larvae

Multiple species can live in the same streams or rivers owning to their specific habitat preferences, resulting in the formation of intricate aquatic food webs.

The adults, on the other hand, live on land. During the day, they often stay in moist and cool regions like riparian vegetation or fly in swarms above the water.

5. Life Cycle

Caddisflies, unlike mayflies, don’t have a nymph phase. They experience complete metamorphosis, going through distinct stages of egg, larva, pupa, and adult. After courtship, females lay their eggs in or around water, employing methods such as walking or submerging themselves in the water.

These eggs are affixed to submerged rocks or plants using a gelatinous substance. Once exposed to moisture, the eggs hatch, and the larvae emerge from the gelatinous matrix. They then proceed to construct cases or silk nets. These cases serve as a shield and camouflage, safeguarding the larvae’s delicate bodies from abrasive surfaces.

The caddisfly egg mass

Caddisflies spend most of their lives as larvae, a phase that can endure for one to two years. Throughout this period, the larvae undergo multiple stages of growth while constructing protective casings or silk nets to ensure their safety and blend into their surroundings.

These creatures possess the remarkable ability to endure extreme winter conditions, with certain species capable of surviving within the ice. During hibernation, they can be either as larvae or eggs. In larval development, the fifth is the longest stage. During this phase, they eat a huge amount of food to prepare for pupation.

The caseless caddis fly larvae/ Cre: Jan Hamrsky

In the pupal stage, caddisfly larvae enclose themselves within their protective cases and experience physical transformations. The length of this stage can differ among species, some may even spend the winter as pupae. When the time comes, they gnaw through their shells to emerge and swim toward the surface of the water.

The adult caddisflies are terrestrial, predominantly active during the nighttime, and actively seek out a mate to reproduce. During the mating process, these organisms partake in a series of behaviors aimed at attracting potential mates. These rituals often include intricate dances, sounds, and chemical signals. The species can mate with different partners.

These insects exhibit diverse lifespans, usually spanning from a few weeks to a year. Larger species may live longer, especially in colder environments.



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