Do Caddisflies Bite? Unraveling the Mystery

Caddisflies are fascinating aquatic insects belonging to the order Trichoptera.

They are small, moth-like creatures, prevalent in a wide range of habitats like streams and rivers, and are a crucial part of the ecosystem.

Many people who come into contact with these insects may wonder if they bite or pose any sort of threat.

While caddisflies may appear somewhat intimidating, they do not bite humans.

They play a vital role in the food chain, mainly serving as prey for various fish and other predators.

Their larvae are essential indicators of water quality, often signaling a healthy aquatic environment.

Caddisflies’ non-threatening nature makes them the perfect study subject for scientists and excellent companions for fly fishing enthusiasts.

So, the next time you encounter these fascinating creatures, you can admire their beauty and ecological importance without worrying about bites.

Caddisflies: An Overview

Insect Classification

Caddisflies are a group of aquatic insects classified under the order Trichoptera.

These insects are often mistaken for moths due to their similar appearance and behavior.

Caddisflies can be found all over the world, with more than 14,500 known species documented.

Some main features of caddisflies include:

• Slender bodies
• Long antennae
• Hairy wings
• Two pairs of wings held roof-like over their bodies

Adult Caddisflies vs Moths

Caddisflies and moths, although similar in appearance, actually belong to two different insect orders.

Caddisflies belong to Trichoptera, while moths are part of the Lepidoptera order.

Here is a comparison of adult caddisflies and moths:

An example of a unique caddisfly species is the Enoicyla pusilla, which is flightless and found in the United Kingdom.

This particular species can be identified by its distinct appearance, habitat preferences, and of course, its inability to fly.

Diet and Feeding Habits

Caddisflies larvae are known to have a diverse diet. The larvae are mainly:

• Aquatic
• Feeding on algae
• Detritus (decomposing plant material)

These small insects are also known to employ different feeding strategies, such as filtering particles from the water and capturing their prey in silk webs.

For example, Brachycentrus spp. caddisfly larvae filter food particles while housed within protective cases made of twigs, leaf fragments, and sand.

Do Caddisflies Bite?

Potential Dangers to Humans

In general, caddisflies are not known to bite humans.

Although some species are attracted to people, most caddisflies do not pose any direct dangers.

In contrast, insects from another order called Diptera, such as black flies, are known to bite humans.

Eastern North America hosts around six black fly species that feed on humans.

Caddisflies vs. Black Flies: Quick Comparison

Life Cycle and Habitats

Eggs and Larvae

Caddisflies are aquatic insects that begin their life cycle as eggs. The eggs are laid in damp areas like pond vegetation or near freshwater habitats.

After hatching, the larvae live underwater and construct a protective case or tube made from silk, tiny plant particles, sand grains, or detritus. Some key features of caddisfly larvae include:

• Aquatic living
• Creating protective cases
• Feeding on algae or other organic materials

Pupation and Adult Stage

As caddisfly larvae mature, they pupate within their cases in preparation for the adult stage. During this stage:

• Cases become sealed for protection
• Adults develop functional wings
• External gills are lost

Once fully developed, adult caddisflies emerge from their cases and are drawn to light sources at night. Adults are mostly harmless, not known to bite humans, and serve as an important food source for aquatic predators like trout.

Comparison of Life Stages:

In conclusion, caddisflies have a fascinating life cycle and occupy distinct habitats as they transition from larvae to adults. Understanding their life stages and habits can provide valuable insight for entomologists and naturalists alike.

Conclusion

Caddisflies, belonging to the Trichoptera order, are intriguing aquatic insects that play a pivotal role in freshwater ecosystems.

Often mistaken for moths due to their similar appearance, these creatures have a unique life cycle, transitioning from aquatic larvae constructing protective cases to winged adults.

While they pose no threat to humans, their larvae serve as vital indicators of water quality and are a crucial food source for many aquatic predators.

Their ecological significance, combined with their harmless nature, makes caddisflies a subject of interest for both scientists and outdoor enthusiasts.

Reader Emails

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

Letter 1 – Caddisfly accused of biting woman

Subject: Just bit me!!
Location: Medford, NJ
July 28, 2014 10:33 am
This bug bit me get I see no pincers or stingers. It has long antenna, long skinny wings, a short body and is greyish in color.
Signature: Anne Marie

Dear Anne Marie,
This looks to us like a Caddisfly in the order Trichoptera, and we would challenge your belief that it stung or bit you.  Most Caddisflies do not have functional mouthparts, and they do not feed as adults. 

According to BugGuide:  “Some adults take liquid food, such as nectar, others do not feed.”  They do not possess stingers either.  Is it possible that you have mistaken this Caddisfly for the creature that bit you?

Letter 2 – Caddisfly

What’s That Bug? 😉
Hi there, bugman!!
Here’s to swamping you some more. Found this little bug/moth? on my wall and wondered what he is. I searched you site a bit, though not very thoroughly as I’m on dial-up most of the time and those lovely photos take aaaaaages to load. 😉 Didn’t find him. Instead of jamming your inbox with image attached, here’s a link to it on my Flickr
account. Best of luck catching up with your email! 😉
Vedrana

Hi Vedrana,
We don’t believe we will ever truly catch up on our emails. There were about 675 letters in our in box when we returned and we began by deleting everything with no subject line and have reduced the number by more than half.

We are trying to post two letters per day from our absence and your linked image was perfect. This is a Caddisfly, a mothlike insect with an aquatic nymph. Caddisflies belong to the order Trichoptera.

Letter 3 – Caddisfly

Order?
I was teaching some orders of aquatic insects along Little River in Van Damme state park (redwood forest; about 1 mile inland from ocean ; Mendocino County) And we saw this black insect. I am embarrassed that I couldn’t even figure out the order. The wings did not look like they had scales.
Thanks!
Teresa Sholars
Professor of Biological Sciences
Science Coordinator
Mendocino Coast Campus
College of the Redwoods

Hi Teresa,
We wish your photo was more detailed. We believe this to be a Caddisfly, Order Trichoptera. Renowned lepidopterist and Mt. Washington neighbor Julian Donahue just confirmed our identification.

Here is what he has to say: “Nice website! I’ve actually been there before, and had already bookmarked it! I just never knew that you were a neighbor. And you’re correct about the caddisfly, although I can’t tell you what family it is.”

Letter 4 – Caddisfly

what’s this bug
Hi, any idea what this bug is? i found it nearby a stream channel. it’s not in my field guide. thanks so much. great web site.
Rebecca McCue

Hi Rebecca,
This is a species of Caddisfly, Order Trichoptera. They resemble moths and are poor fliers. Larvae are aquatic and the larvae build homes by cementing sticks and stones together, forming a tube which is used as protection as well as camoflauge. There are over 1000 species in North America. Sorry I can’t give you an exact species.

Letter 5 – Caddisfly

playground bugs [part 2]
Dear BUGMAN,
Thank you for writing back to us! WE LOVE YOUR SITE!!!!!
We are sending two medium sized photos of our Caddisfly [we thought the other photo we sent might be too small to be seen on the site]. We hope they help others!

We also included our favorite stag beetle photo and praying mantis photo [it stayed on the wall next to our classroom door for days! We think it was listening in!] Thank you again for your help!
Always looking for bugs, Fours and fives in PA

Dear Fours and Fives in PA,
Thank you for the additonal photos. We are posting them immediately.

Letter 6 – Caddisfly

What are these playground bugs?
Hello!
We are so happy to have found your web site! We are a class of 4 and 5 year olds in PA. We take photos of bugs everyday but then we have no clue what they are. We used the photos on your site to identify some of the bugs we have photographed. Like the Wheel Bug that visited us last week.

The second photo is of a bug we have not named yet so hopefully we can start off calling it the proper name. We like its funny “nose”. Obviously we REALLY need a bug encyclopedia! THANK YOU VERY VERY MUCH!
Fours and Fives in PA

Dear four and five year olds,
I’m so happy to see you are budding entomologists. Your other insect is a Caddisfly. They are members of the order Trichoptera that begin life as aquatic larvae. The larvae construct homes from sticks and tiny pebbles which are cemented togethe, acting as both protection and camouflage. The larvae are sometimes called Caseworms.

Letter 7 – Caddisfly

long winged fly
June 5, 2009
Found this last night sitting on the window sill near the side porch. It was not alarmed by me getting quite close to it, it did not move much at all. It was between 1.5 and 2 inches long.
J Reben
Fairfield, Maine, USA

Dear J,
We are catching up on old mail, and there are some gems we never had the time to address.  Your photo is one of those.  This is a Caddisfly in the order Trichoptera.  The adults are often compared to moths, and the aquatic larvae are known as Caseworms.

We believe your large Caddisfly is Hydatophylax argus, a species with no common name, but in the family Limnephilidae, the Northern Caddisflies.  You can see some matching images on BugGuide.

Letter 8 – Caddisfly

ong nosed insect
May 8, 2010
This guy was hanging out near out back door porch light. It’s 4 in the afternoon, and he hasn’t moved much at all since before lunch. He’s about 2 and half to three inches long, including his portruding proboscis.

Light brown color on wings, eyes look like black points raised slightly and forward of head. His proboscis is nearly as long as his body, slightly curved downward.
Joe
Black Diamond, WA (Pacific Northwest)

Hi Joe,
This is a Caddisfly, a mothlike insect with a casemaking aquatic larva.  It is in the order Trichoptera, which is well represented on BugGuide, but we haven’t a clue as to its family, genus or species. 

What you are calling a proboscis is actually antennae.  We apologize for the lengthy time it took us to respond, but we were out of the office for a week and we are still behind in our mail.

Letter 9 – Caddisfly

Subject: Seattle Mystery Bug
Location: Seattle WA
February 1, 2013 7:55 am
I was wondering if you could tell me what this brown flying insect is, as seen in a Pacific Northwest living room on 01/31/2013. I’ve never seen one of these before, and now this is the second one I’ve found inside a house in two days.

It may be very common, but is new to me. It’s brown and about 1 1/2” long. The pattern on the wings makes it look like it is made of wood. I thought it was a moth when it first flew by, but it is sort of slow moving, a clumsy flier, and heavier. Any thoughts?
Signature: A

Dear A.,
You have had an encounter with a Caddisfly in the order Trichoptera, and as we learned from BugGuide, there are:  “1,350 spp. in ~150 genera of 22 families in NA [North America]” and we cannot say for certain how to classify it more specifically, though it does closely resemble several photos from the genus Psychoglypha that can be found on BugGuide. 

Like you own observations, BugGuide notes that “Adults resemble moths, but wings are hairy instead of scaly.”  Larval Caddisflies are aquatic and they construct shelters, so they are commonly called Caseworms.  Interestingly, each species of Caddisfly Larva builds a different shelter, some of sticks, some of stones, some of shells and others from other materials. 

According to bugGuide:  “Most species live in a mobile case constructed from plant material, algae, grains of sand, pieces of snail shells, or entirely of silk. The case is held together with strands of silk secreted by the larva. In some species the case is attached to a rock, log, or other underwater surface; a few species have no case and are free-living. 

The case’s particular shape and construction material is distinctive of the family and/or genus, and can be used in identification. Example: Helicopyschidae larvae use sand grains to build spiral cases that resemble small snail shells.”

You are amazing! Thanks so much for the response. Mystery solved.

Letter 10 – Caddisfly

Subject: What is this bug?
Location: Near Darrington, WA
October 20, 2013 6:55 pm
Hello!
I found this bug near the Sauk River in Washington State. If you are able to identify it, I’d be very happy.
Signature: Darcy

Hi Darcy,
We hope an insect order will suffice.  This is a Caddisfly in the order Trichoptera.  According to BugGuide, there are:  “>1,350 spp. in ~150 genera of 22 families in NA” and we haven’t the necessary skills to provide a more specific taxonomy than the order. 

Caddisflies are feeble fliers and they are often confused with moths.  Because they cannot fly great distances, they are generally found not far from water where the aquatic larvae develop. 

Caddisfly larvae often build distinctive shelters from pebbles, shells, twigs and other aquatic detritus, and for that reason they are frequently called Casemakers or Caseworms.  Freshwater anglers use Caddisfly larvae as bait. 

Letter 11 – Snow Sedge

Subject: Help us identity this bug
Location: Sedro Woolley, WA
January 9, 2014 4:57 pm
What’s this bug? Can’t tell from the picture, but it has 3 white lines on it’s wings. The picture was taken, 1/9/14 which is winter for us in the Pacific Northwest.
Signature: Elizabeth

Dear Elizabeth,
This is a Northern Caddisfly or Snow Sedge.  Caddisflies are often mistaken for moths, and according to BugGuide:  “Adults resemble moths, but wings are hairy instead of scaly.” 

Caddisflies also share some behavioral characteristics with moths.  According to BugGuide:  “flight activity begins at dusk. Adults are attracted – sometimes in great numbers – to artificial light.” 

Larvae, which are commonly called Caseworms, are aquatic, and of the habitat, BugGuide notes:  “Species most diverse in well-aerated streams, but also occur in lakes, ponds, and marshes.”

Thank you so much, Daniel Marlos!!

Letter 12 – Caddisfly

Subject: unknown caddisfly
Location: Toronto, Ontario, Canada
June 2, 2014 6:14 pm
I know that this is a caddisfly, any idea what genus or even species? Do you have any good resources that are user friendly in regards to identifying caddisflies?
Signature: Gary Yankech

Dear Gary,
This is a marvelous image of a mothlike Caddisfly, but we don’t know its species, we find the identification of Caddisflies to the species level to be something outside of the range of our present abilities, and we don’t know a Trichopterist.  We will do a quick look on BugGuide to see if anything jumps out at us.  Both this similar looking individual on BugGuide and this similar looking individual on BugGuide are only identified to the order Trichoptera.

Update and Offer to identify Caddisflies:  July 27, 2014
Subject: trichoptera ID
Website: ncwildlife.com
July 27, 2014 6:40 am
Hi bug people!
I love your site, just stumbled on to it trying to get info in phoretic mites on a Holoptera beetle I found yesterday.
While perusing your site, I noticed several partially IDed caddisflies and the statement that you don’t currently know a trichopterist.  Well, I don’t lay claim to the title trichoperist these days, but I’ve spent many years studying them, have many identification resources on hand, and still quite a bit of personal memory about many caddisflies.

I’m also still personally connected to and correspond with many of the the few working trichoperists in the US.  I also co-authored a checklist of caddisflies of Tennessee several years ago (Etnier, D.A., J.T. Baxter, S.J. Fraley, and C.R. Parker. 1998. A checklist of the caddisflies of Tennessee. Journal of the Tennessee Academy of Science 73:53–72.).

I’m currently a working aquatic biologist focussed mainly on the conservation and restoration of native fishes, mussels, and crayfishes, but continue to pay attention to bugs, if not study them any more.
The upshot is I’d be glad to take a whack at IDing caddisflies for folks, if you still need some help.
Best to you,
Steve
Signature: Steve Fraley

Hi Steve,
We would gladly welcome any family, genus or species identifications on Caddisflies in our archives.  Please post comments on anything you are able to identify.

Letter 13 – Caddisfly

Subject: brown buggy
Location: Southeastern Michigan
August 15, 2014 8:29 pm
I found this floating in a casserole dish in my sink today. I just can’t pinpoint it! I recently found a masked hunter adult in my house and am on edge about all our six legged and more friends.
Signature: confused

Dear confused,
This Caddisfly in the order Trichoptera is perfectly harmless.  Adult Caddisflies are sometimes confuse with moths which they superficially resemble.  Caddisflies have aquatic larvae known as Caseworms because they build shelters.

Letter 14 – Caddisfly

Subject: We think it is a…
Location: Wilkes-Barre, PA
October 13, 2014 6:43 pm
Hello Bugman!
My son and I found this interesting critter on our back porch this evening. We believe it is a Northern Caddisfly, but wanted an expert opinion to let us know if we are right or wrong. From a decription we found online, we are happy to find this Caddisfly.

We live along the Susquehanna River in Northeastern Pennsylvania. The river has developed a reputation for not being very clean, but if this Caddisfly is any indicator, as it is purported to be, the river is starting to heal. Thanks for your advice!
Michael Raub
Wilkes-Barre, PA
Signature: Michael Raub

Dear Michael,
We believe your identification of this Caddisfly is spot on, though we are very reluctant to attempt a species identification with most Caddisflies.  You are correct about Caddisflies being an indicator species for clean water.

Letter 15 – Caddisfly

Subject: Moth?
Location: Vermilion County, Illinois
September 3, 2015 9:41 am
Hello Bugman,
I found this insect on my office window – I work at a park in East Central Illinois. At first, I thought it could have been a species of snout butterfly, but realized after getting up close – they were antennae. But I don’t know if I’ve ever noticed moths/butterflies having their antennae closed together.

It was a cool morning, dew on the grass, light low-laying fog, but he appeared dry and content on my window. Any idea what this could be so I can learn more about this species? Thanks so much!!!
Signature: Lara the NatureNerd

Dear Lara the NatureNerd,
Though you were wrong about the identification, you were quite astute to notice the morphological similarities between this Caddisfly and some moths. 

Caddisflies begin life as aquatic Caseworms.  Though it is not in a natural setting, we really love your Caddisfly image because of its simplicity, but we did adjust the levels and rotate.

Letter 16 – Caddisfly

Subject: Garden bug
Location: Dorset uk
April 8, 2016 4:15 am
Found this in Dorset UK , it’s spring
Signature: Karen

Dear Karen,
This is a Caddisfly, a member of the insect order Trichoptera, a group of mothlike insects with aquatic larvae known as Caseworms.  Because their larvae are aquatic, and because Caddisflies are not strong fliers, they are generally found not far from a source of fresh water.

Letter 17 – Caddisfly

Subject:  What is this creature?
Geographic location of the bug:  Hartford County, Connecticut
Date: 09/24/2017
Time: 08:55 PM EDT
Hellooooo Bugman. It’s great to see your site as active as ever. I sent you an inquiry years ago and you were able to help. Thank you! Could you please help again? We have been seeing several of these guys and I thought they were roaches at first!

The body looks more like a moth to me, but the antennae look more like a beetle. The wings stand up at an interesting angle.
How you want your letter signed:  Thanks again! Annie

Dear Annie,
This is a Caddisfly, and your observation that it resembles a moth is understandable.  Entomologists tend to agree that the Caddisfly order Trichoptera does share many similar traits with the Moth order Lepidoptera.  Do you live near a body of water?  The nymphs of Caddisflies are aquatic and they are commonly called Caseworms.

Letter 18 – Caddisfly

Subject:  Bugs all over the house
Geographic location of the bug:  Upstate, SC
Date: 04/16/2019
Time: 05:33 PM EDT
Your letter to the bugman:  Our neighbors and I are trying to figure out what type of bug this is. They have recently exploded in our neighborhood and we’ve never seen them before.
How you want your letter signed:  Confused new home owner

Dear Confused new home owner,
You have no cause for concern.  Do you live near a body of water?  This is a Caddisfly.  Caddisflies have aquatic larvae that are known as Caseworms that are used as bait by many fishermen. 

Letter 19 – Bug of the Month April 2020: Caddisfly Larva from the UK

Subject:  Spikybugs in garden pond
Geographic location of the bug:  Norfolk, United Kingdom
Date: 03/23/2020
Time: 08:29 AM EDT
Your letter to the bugman:  Hello, At first I thought these creatures were pieces of pond weed. However, on observing them for 10 minutes or so, I see they are ALIVE and they appear to be interacting with each other.  The are located in one small part of a garden pond.

They appear to have a sucker on one end. I replaced the bug in the photo back in the pond! Thank you for any help in identification.
How you want your letter signed:  Jo

Dear Jo,
This is the larva of a Caddisfly, an aquatic naiad that will eventually metamorphose into a flying insect that somewhat resembles a moth.  Caddisfly larvae construct a shelter from twigs, shells, pebbles, and other debris, and different species of Caddisflies construct different types of cases.  This image on Ed Brown Wildlife and Nature Photography looks exactly like your individual.  We are making your submission our Bug of the Month for April 2020.

Letter 20 – Caddisfly

Subject:  Moth-shaped fly?
Geographic location of the bug:  Scotland
Date: 08/12/2021
Time: 08:00 AM EDT
Your letter to the bugman:  Hi bugman! This flew into my house late at night in august. It has clear wings like a fly, but shape-wise it holds itself like a moth! And very long antennae! Any idea?
How you want your letter signed:  Indrid

Dear Indrid,
This Caddisfly does share many physical traits with Moths.  According to the North American insect identification site BugGuide:  “Adults resemble moths, but wings are hairy instead of scaly.”