Caddisfly Life Cycle: A Fascinating Journey from Larva to Adult

Caddisflies are fascinating insects belonging to the order Trichoptera, with a unique life cycle that begins in water.

These aquatic insects undergo a series of developmental stages, growing and changing from larvae to pupae to adults as they progress.

In the larval stage, caddisfly larvae are commonly found in flowing waters, living on the bottom surfaces of streams and constructing tubes or cases out of sand, pebbles, or leaves for protection.

These resourceful insects demonstrate their ability to adapt to their environment, eventually transforming into pupae within their aquatic homes.

Caddisfly Overview

Trichoptera Classification

Caddisflies belong to the insect order Trichoptera, which is a large category with many species.

The name “Trichoptera” comes from Greek words, with “tricho” meaning hair and “ptera” meaning wings, referring to their hairy wings.

Physical Characteristics

Caddisflies are typically small to medium-sized insects. Adult caddisflies resemble moths, with some key differences:

• Hairy wings instead of scaly wings
• Dark and drab colors
• Long, threadlike antennae, often as long as the body itself

Habitats

Caddisfly larvae (aka caddis flies) mostly live in:

• Flowing waters
• Bottom surfaces of streams

These aquatic larvae often construct protective cases or tubes using materials like sand, pebbles, and leaves.

This trait helps distinguish caddisfly larvae from other aquatic insects.

Comparison Table: Caddisflies vs. Moths

Feature	Caddisflies	Moths
Wings	Hairy, dark, and drab	Scaled, often colorful
Antennae	Long, threadlike, many-segmented	Varies by species
Aquatic lifecycle	Larvae live in water, build cases	Not associated with water

Caddisflies undergo a life cycle involving egg, larval, pupal, and adult stages.

Females lay eggs near water, and the larvae develop through four stages called instars before pupating.

Their pupation is nearly always aquatic, and adults are typically short-lived, focusing on mating or laying eggs.

Caddisfly Life Cycle

Mating and Egg Laying

The mating and egg-laying process of caddisflies has its own set of interesting behaviors:

• Female caddisflies lay eggs in gelatinous masses, often on vegetation near water.
• Nymphs emerge from the eggs and start building protective cases for themselves.

Eggs

Caddisflies begin their life cycle as eggs, which are typically laid by females near the water’s edge or by dipping their abdomen into the water surface.

The eggs then develop and hatch into larvae.

Larvae

Caddisfly larvae, also known as caddis larva, are small, aquatic insects in which they undergo different stages of development, known as instars.

These larval stages typically occur over several months or even a year.

• Habitat: Caddisfly larvae live in flowing waters, often constructing tubes or cases from sand, pebbles, or leaves to protect themselves.
• Diet: They feed on organic matter, such as leaves or small organisms like plankton and other insects.

Pupae

After the larval stage, caddisflies enter the pupal stage. During this stage, they prepare for their transformation into adults.

• Location: Pupation is almost always aquatic.
• Duration: The pupal stage can last anywhere from a few days to several weeks, depending on the species.

Adults

Finally, caddisflies emerge as winged adults, which are short-lived and spend most of their time focusing on mating and laying eggs.

Adult caddisflies go through complete metamorphosis, resulting in a significant physical difference between the adult and larval stages.

They are often nocturnal, with some species being attracted to light.

Life Cycle Stage	Duration	Characteristics
Eggs	–	Laid near water’s edge
Larvae	Several months to a year	Aquatic, build protective cases, undergo instars
Pupae	Days to several weeks	Prepare for transformation into adults, aquatic
Adults	Short-lived	Mating and laying eggs, undergo complete metamorphosis, nocturnal

Feeding and Diet

Larval Diet

Caddisfly larvae are aquatic creatures with a unique diet. They primarily feed on:

• Plants: Small fragments of aquatic plants serve as their main food source.
• Algae: These tiny organisms are common in water environments.

Adult Diet

Once caddisflies mature into adults, their diet changes. They mostly consume:

• Nectar: As a primary food source, nectar provides energy for adult caddisflies.

Some characteristics of adult caddisflies include:

• Moth-like appearance
• Roof-like wing position
• Dark colors

Comparison between larvae and adult caddisfly diets:

Stage	Main Food Source	Other Food Sources
Larvae	Aquatic plants	Algae
Adult	Nectar	None

Remember, a healthy caddisfly population contributes to a balanced aquatic ecosystem, as their unique diets help maintain water environments.

Adaptations and Behaviors

Protective Cases

Caddisfly larvae are fascinating creatures known for their unique adaptation of building portable protective cases.

These cases help shield the larvae from predators, as they remain hidden inside them.

Larval Case

A famous caddisfly species, Brachycentrus spp., filters food particles from water while staying inside their protective cases, which they build themselves using twigs, leaf fragments, and sand.

Here are a few features of protective cases caddisfly larvae build:

• Made from tiny pieces of plants, sand grains, or other detritus
• Adhered or spun together into tubes or cones

Flight and Movement

Caddisflies are insects with strong, hairy wings, which they use for flight and movement.

They have four wings covered in hairs that allow them to flutter and fly with ease.

Their bodies are equipped with structures like antennae and hairs for better mobility and sensing.

Caddisflies and the Environment

Water Quality Indicators

Caddisflies are sensitive to water quality, making them excellent indicators of water quality in streams, rivers, lakes, and ponds.

Their presence usually indicates clean, well-oxygenated water.

For example, a diverse caddisfly population would be a sign of a healthy aquatic ecosystem.

Habitat Preferences

Caddisflies are aquatic insects found in various water bodies such as:

• Streams
• Rivers
• Lakes
• Ponds

These invertebrates prefer habitats with:

• Clear, flowing water
• Vegetation
• Rocks, wood, or sand on the bottom

Ecological Roles

Here are some ecological roles caddisflies play:

• Serve as food for fish, birds, and other animals
• Assist in breaking down organic matter and recycling nutrients
• Indicate overall health of aquatic ecosystems

Comparison of Aquatic Insects:

Insect	Habitat	Indicator of Water Quality	Metamorphosis
Caddisflies	Streams, rivers, lakes, ponds	Yes, sensitive to changes	Complete
Dragonflies	Similar to caddisflies	Less sensitive than caddisflies	Incomplete

In conclusion, caddisflies are integral parts of aquatic ecosystems.

Their habitat preferences and sensitivity to water quality make them important water quality indicators.

Understanding caddisflies’ ecological roles and life cycles can help us monitor and preserve these aquatic habitats for future generations.

Predators and Threats

Common Predators

Caddisfly larvae are a major food source for a variety of predators in their aquatic habitats. Some examples of common predators include:

• Bats: These nocturnal mammals are known to feed on adult caddisflies flying near the water surface at night.
• Birds: Many bird species, such as flycatchers and swallows, catch caddisflies in mid-air or prey on their larvae in the water.

Environmental Threats

Caddisflies are sensitive to changes in water quality and flow. Some environmental threats impacting their populations in North America include:

• Water pollution: Contaminants like pesticides, fertilizers, or heavy metals can harm caddisfly larvae, affecting their survival and reproduction.
• Altered water flows: Changes to water flow, such as those caused by dams, can disrupt caddisfly larvae habitats or wash away their cases, leading to reduced populations.

Threat	Impact on Caddisflies
Water pollution	Adversely affects survival and reproduction, leading to decreased populations
Altered flows	Disrupts habitats, washes away cases, and may lead to population reductions due to changed conditions

Conclusion

In summary, caddisfly life cycle consists of four stages:

• Egg: Females lay eggs on the water’s edge or dip their abdomen into the water surface¹.
• Larva: Aquatic larvae develop through four instars, typically within protective cases².
• Pupa: Pupation occurs in most cases underwater³.
• Adult: Short-lived adults primarily focus on mating and laying eggs⁴.

Some characteristics of caddisfly larvae include:

• Slender body
• Segmented abdomen
• Chewing mouthparts
• Three pairs of legs
• Protective cases made from plants, sand grains, or detritus⁵

By understanding the caddisfly’s life cycle and its unique features, we can better appreciate their role in the ecosystem and work to protect their habitats.

Footnotes

1. https://texasinsects.tamu.edu/trichoptera/caddisfly/ ↩
2. https://education.mdc.mo.gov/discover-nature/field-guide/caddisfly-larvae ↩
3. https://texasinsects.tamu.edu/trichoptera/caddisfly/ ↩
4. https://texasinsects.tamu.edu/trichoptera/caddisfly/ ↩
5. https://education.mdc.mo.gov/discover-nature/field-guide/caddisfly-larvae ↩
6. https://education.mdc.mo.gov/discover-nature/field-guide/caddisfly-larvae ↩
7. https://education.mdc.mo.gov/discover-nature/field-guide/caddisflies ↩
8. https://www.epa.gov/caddis/basic-information-about-caddis ↩

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Caddisfly from Canada

Subject: What is this?
Location: Calgary Alberta Canada
June 20, 2016 9:10 pm
Hi, I live in Calgary Alberta Canada and now noticed the follow fly, which generally appears in swarms around the house or spruce trees. Flies are out from June to August/September.

The only come out I the late afternoon or evening when the temperature begins to cool. During the day they rest on the side of the house or along the soffits.

House backs onto a green space and is roughly 100 yards from the bow river. Swarms have become larger in recent years and I’d love to know what they are. They do not bite or sting. Just very annoying and unsightly.
Thanks for your help!
Signature: Angela

Dear Angela,
This is a Caddisfly, a member of the order Trichoptera.  Caddisflies are often described as “mothlike” and the fact that you are so close to the river explains why you have so many Caddisflies in your yard.  Immature Caddisflies, sometimes called Caseworms, are aquatic, frequently used as live bait by anglers, and according to BugGuide: 

“Most caddisfly larvae are intolerant of pollution; therefore, their presence is an indication of good water quality, and their absence in areas where they previously occurred may be an indication of polluted water.”  Caseworms make cases from a variety of materials, including sticks, sand, pebbles, snail shells, bits of leaves and many other materials, however, each species is very specific about the material used and the shape of the case. 

BugGuide also notes:  “Adults rest on nearby vegetation during the day; flight activity begins at dusk. Adults are attracted – sometimes in great numbers – to artificial light” and that agrees perfectly with your account.  More information on Caddisflies can be found on Aquatax where it states: 

“Probably the most interesting feature to the non-fishing general public regarding this group is the cases that many of the larvae construct out of various materials. Caddisflies are found in all types of aquatic habitats throughout Saskatchewan. The majority are intolerant of pollution and, as such, are valuable tools for monitoring organic and chemical contamination of habitats.”

Letter 2 – Caddisfly found in the Snow: Snow Sedge perhaps

Winter Critters
December 30, 2009
I took a walk in the woods this month in western New York and found many little critters on top of the snow. I would appreciate any help you might be able to give in identifying.

The trails are on a 600-acre wetland preserve and most of the pictures were taken in mixed woods of pine, hemlock, cherry, maple, oak, etc. that surround a very slow-moving marshy pond.
All of the pictures can be found on my blog (which links to bigger versions on Flickr): http://winterwoman.net/2009/12/23/snow-critters/
There were some spiders, too… Can you help with them?
Thanks in advance for your help!
Jennifer Schlick
Wetland preserve, western New York State on Dec 22, 2009

Hi again Jennifer,
Your third image is of a Caddisfly, but we don’t want to try to identify it any further than the order Trichoptera, or possibly the Northern Caddisfly family Limnephilidae.  We did find a reference on a fishing website to Winter Caddisflies in the genus Psychoglypha that are called Snow Sedges. Troutnut.com also has this comment posted: 

“Dr. George Roemhild explained to me how he finds these winter caddisflies in February and March: ‘They crawl up on the snowbanks, but when the sun hits their dark wings they melt down out of sight. That’s how I collect them, by walking along looking for holes in the snow.'”

We also found a reference to Snow Sedge on the Flyfishing Entomology website, our new favorite etymology reference page.  Your second image, the caterpillar, is some species of Cutworm.

Wow.  You’re my hero.  thanks a billion.  Now I’m going to have to write a blog post about the wonderful folks over at What’s that Bug!!!

Here’s my blog post:
http://winterwoman.net/2009/12/31/whats-that-bug/
Thanks again!

Letter 3 – Caddisfly from Alaska

Is this a termite?
Location: Nome, AK
August 14, 2011 2:28 pm
I’ve seen two of these in my house in Nome Alaska. Is it a termite?
Signature: TJ

Dear TJ,
This is not a termite.  It is a Caddisfly in the insect order Trichoptera.  The aquatic larvae are called Casemakers, and they build homes from sticks, plant material, sand, shells and other materials.  Each species has a very distinctive case.  You may also search Bugguide for additional information.

Letter 4 – Caddisfly from Canada

October moth?
Location: Port Coquitlam, BC, Ca
January 19, 2012 11:40 pm
This (moth?) sat unmoving for several hours on the key guard of a near-by door. I really wanted a look at the abdomen, but thought it unfriendly to poke at it. Total legnth of about 5 cm, including antennae. Photos taken on October 5/11.
thank you!
Storm Vos-Browning
Signature: Storm

Hi Storm,
Though it is mothlike, this insect is actually a Caddisfly in the order Trichoptera.  Caddisflies have aquatic larvae that carry cases about with them earning them the common name of Caseworm.

Hi Daniel,
For a small team with a backlog, you sure answered my question FAST! Thak you. The forward pointing antennae looked wrong for a moth, as did the mouth parts, but I’m not very good at identifying insects.

Love watching them, though – I’ve spent hours watching caddisfly larvae in local waterways, but didn’t know what the adults looked like.
As with the stink bug nymph you ID’ed for me back in August, I’ll post a link to What’s That Bug? when I post the photo on my blog.
best wishes,
Storm

Thanks for the positive comments Storm.  So, you raise Killies?  The African Aphyosemion species are really spectacular fish.  We have our own Angelfish aquaria going.  We are sticking to Amazon species for now.

Wow, Daniel, you actually checked out the link? No one ever does that!
“Amazon species” is a huge category – you’ll never run out of cool species. I’m personaly captivated by the small, nocturnal driftwood cats, the corydoras and farlowellas.

The unidentified critter Lori asks about at the bottom of the page looks to be a seed shrimp (Ostracod) but the photo is indistinct. I don’t know how you manage to ID bugs from photos!
you run an awesome site!
cheers, Storm

Letter 5 – Caddisfly in the Snow!!!

Subject: Bug ID
Location: Bridger Mountains, Montana
January 24, 2017 4:00 pm
This bug was found outside of Bozeman, Montana, in the Gallatin National Forest. A nordic skier was skiing down an unplowed road and saw the bug walking on top of the snow. Nearby tree species include Douglas-fir, Engelmann spruce, lodgepole pine, and subalpine fir.
Signature: Johanna Nosal

Dear Johanna,
This is a Caddisfly, an insect in the order Trichoptera that is generally found near a source of fresh, clean water because their larvae are aquatic nymphs sometimes called Caseworms because they build protective covers from sticks, stones or shells.  It is our understanding that Caddisflies found in the snow are known as Snow Sedges. 

We found this reference to a Snow Sedge on BugGuide, however the information page for the genus on BugGuide does not indicate Snow Sedge is a common name.  TroutNet does identify Snow Sedges and has this to report: 

“These caddisflies may be important to the winter angler because they are one of the only insects around.”  Your posting has inspired us to create a “Snow Bugs” tag because we have numerous postings in our archive of insects in the snow, though it was not until now that we decided to organize them together into a dedicated data base.

Letter 6 – Caddisfly from Canada

Subject:  Autumn Brown Bug
Geographic location of the bug:  New Brunswick, Canada
Date: 09/16/2017
Time: 08:34 AM EDT
These bugs just started coming around recently as the weather starts to change these bugs started to come around everywhere!! What are they?!
How you want your letter signed:  Thanks, Danielle

Dear Danielle,
This is a Caddisfly in the order Trichoptera.  Caddisfly nymphs are aquatic and they are frequently called Caseworms as they construct often elaborate protective cases from twigs, sand and shells.  Since the nymphs are aquatic, we suspect you live near a body of fresh water.  Your submission is the second we are posting this morning from New Brunswick, Canada. 

Letter 7 – Caddisfly from Austria

Subject:  Evening Visitor
Geographic location of the bug:  Central Austria
Date: 10/08/2018
Time: 02:24 PM EDT
Your letter to the bugman:  Dear Daniel, it’s a cool fall evening here in Austria and I opened my windows just to get a little fresh air. Suddenly, this little fella started circling the overheard lamp. I thought it was a moth based on its behavior, but it landed and it’s clearly not a moth. It’s about 2 inches  long with the antennae. Any idea what it is?
How you want your letter signed:  N. Fritz

Dear N. Fritz,
This is a Caddisfly in the order Trichoptera, and they really do resemble moths.   Caddisflies have aquatic larvae known as Caseworms that build shelters for themselves from twigs, pebbles or shells with each species making a very specific type of case.