Moths are often misunderstood creatures, commonly perceived as nocturnal nuisances. But are Moths dangerous, or is this just a myth?
While there are approximately 160,000 species of moths worldwide, many wonder if these insects pose any danger to humans or their environment.
In general, moths are not dangerous to humans. Only a small number of the thousands of moth species can sting or have caterpillars that deliver painful bites.
For example, the puss caterpillar—the larvae of the flannel moth—has been known to cause harm to people when touched.
However, this species is found mainly in southeastern North America, and its presence is limited throughout the year.
Moths can present an environmental threat, as seen with the Spongy Moth or formerly known as the European gypsy moth.
The caterpillars of this species are known for their voracious appetite, consuming over 300 different types of trees and shrubs. As such, they can significantly damage forested areas across North America.
Understanding Moths
Moth vs Butterfly
Moths and butterflies both belong to the insect order Lepidoptera. While they share many similarities, they can be distinguished by specific features:
- Antennae: Moths have feathery or filament-like antennae, while butterflies have club-shaped antennae.
- Wings: Moths usually fold their wings over their bodies when resting, whereas butterflies typically hold them upright.
- Activity: Moths are usually active at night (nocturnal), while butterflies are active during the day (diurnal).
| Feature | Moth | Butterfly |
|---|---|---|
| Antennae | Feathery or filament-like | Club-shaped |
| Wings | Folded over body | Held upright |
| Activity | Nocturnal | Diurnal |
Life Cycle
The life cycle of moths consists of four stages:
- Eggs: Female moths lay eggs on host plants.
- Larvae (caterpillars): The eggs hatch into larvae that feed on the host plants, growing and molting several times.
- Pupae (cocoon): The fully-grown caterpillar forms a protective cocoon around itself to develop into an adult moth.
- Adults: The adult moth emerges from the cocoon and begins searching for a mate to repeat the cycle.
Moth Species
There are approximately 160,000 species of moths worldwide, compared to 17,500 species of butterflies. Moths display a wide range of colors and patterns in their wing markings. Some examples of moth species include:
- Spongy Moth: Adults have a wingspan of up to 2 inches, with females being nearly white and males being brown with darker patterns on their wings. Female spongy moths are not capable of flight (USDA APHIS).
- Giant Silk Moths: These large moths have wingspans of up to 6.5 inches. The Polyphemus Moth is a well-known example of this family (PNW Moths).
- Hawk Moths (also known as Sphinx Moths): These moths have heavy bodies and can be quite large. Some hawk moth species are even known for their hovering behavior during feeding.
Are Moths Dangerous?
Physical Danger
Moths, in general, are not physically dangerous to humans.
Most adult moths do not have biting mouths or any form of stinging elements like ants or wasps would.
Moths mainly feed on nectar using their proboscis, a tubular mouthpart similar to a straw. However, some moth caterpillars (larvae) can cause issues due to their defensive features, such as:
- Spines or hairs that can cause irritation
- Toxic compounds in some varieties
For example, the browntail moth caterpillar has tiny poisonous hairs that may cause dermatitis, similar to poison ivy, in sensitive individuals.
Health Risks
While moths themselves are not significant health threats, they can be considered pests.
Some moth species, like the spongy moth (formerly known as the European gypsy moth), are invasive and can defoliate various tree and shrub species, indirectly causing harm to local ecosystems.
Source: Lymantria dispar. (2023, August 18). In Wikipedia. https://ift.tt/RrLq5XW
Vampire moths are an interesting case, as they do have specialized mouthparts adapted for piercing and feeding on blood from mammals. However, these moths are rare and not found in the United States.
| Item | Moths | Ants |
|---|---|---|
| Dangerous to humans | No (usually) | Yes (some species) |
| Bite/Sting | No | Yes (some species) |
| Health risks | Varies by species | Varies by species |
In summary:
- Most moths pose no direct physical danger to humans
- Some caterpillars can cause irritation or have toxic compounds
- Moths can be pests and indirectly affect ecosystems, like the spongy moth
- Rare vampire moths can feed on mammal blood, but are not found in the US
Damage and Nuisance Caused by Moths
Clothes Moths
Clothes moths are common pests that are attracted to various fabric materials.
Their larvae feed on hair, fur, and clothes, causing damage to textiles and clothing. Examples of materials prone to this infestation include:
- Cotton
- Wool
- Linen
- Synthetics mixed with natural fibers
Adult clothes moths don’t actually eat fabrics, but their larvae do.
A moth infestation in stored clothing can result in holes and weakened fabrics, causing frustration and financial loss.
Pantry Moths
Pantry moths are another type of moth that can create a nuisance in households.
They infest dry goods such as cereals, grains, and flour, which can lead to contamination of pantry food. Some characteristics of pantry moths include:
- Attracted to light
- Lay eggs in dry food products
- Able to chew through packaging
Contamination by pantry moths results in wasted food and the need for thorough cleaning.
To avoid infestations, store food in airtight containers and promptly address any pantry moth sightings.
Effects on Gardens
Moth caterpillars can cause damage by feeding on garden plants, affecting leaves, flowers, and fruits.
Some moth species have distinct patterns and specific host plants, making them easy to recognize.
Moth caterpillars can be detrimental to agriculture and may require control measures to protect crops.
| Moth Type | Damage to | Examples |
|---|---|---|
| Clothes Moths | Fabric materials | Clothing, furs, upholstery |
| Pantry Moths | Dry goods | Cereals, grains, flour |
| Moth Caterpillars | Garden plants and crops | Leaves, flowers, fruits |
In summary, moths can be a nuisance and cause damage in various situations. Proper storage and prompt action can help minimize their impact on our lives.
Moths and Human Health
Allergies and Skin Reactions
Moths, particularly their caterpillars, can cause allergic reactions and skin conditions in some individuals. This is often due to:
- Dust: Tiny scales from moth wings can become airborne and trigger allergies.
- Caterpillar hairs: Irritating hairs can cause skin rashes, a condition known as lepidopterism.
Examples of moths that cause skin reactions include the browntail moth and spongy moth.
Caterpillar Dermatitis
Caterpillar dermatitis is a skin condition caused by contact with hairy or spiny caterpillars. Symptoms include:
- Redness
- Swelling
- Itching
- Blisters
Some butterfly caterpillars can also cause similar reactions.
| Moth/Butterfly Caterpillars | Allergic Reactions | Caterpillar Dermatitis |
|---|---|---|
| Moth Caterpillars | Yes | Yes |
| Butterfly Caterpillars | Rare | Yes |
To reduce the risk of caterpillar dermatitis:
- Avoid direct contact with caterpillars
- Wear gloves when handling plants and trees
- Keep pets away from infested areas
Prevention and Management of Moth Infestations
Preventing Moth Infestations
To prevent moth infestations in your home and garden, follow these simple steps:
- Store food properly: Keep nuts, grains, and other moth-attracting foods in airtight containers.
- Maintain cleanliness: Regularly vacuum and clean your home to remove dirt and possible food sources.
- Launder clothing and bedding: Wash wool, feathers, and other fabrics that moths may be attracted to.
- Use repellents: Introduce natural moth-repelling plants, such as poisonous plants, to deter moths from your garden.
Eliminating Existing Infestations
In case you already have a moth infestation, here are some methods for elimination:
- Introduce natural predators: Birds and spiders can help control moth populations.
- Eliminate other pests: By controlling cockroach and spider populations, you reduce their competition for resources, making your home less attractive to moths.
- Use traps: Pheromone traps can help capture and control moths, especially in confined spaces like closets.
Pros and Cons of Different Methods
| Method | Pros | Cons |
|---|---|---|
| Natural predators | Eco-friendly, low maintenance | Can take time to eliminate moths |
| Pest elimination | Reduces overall pest populations in the home | Does not directly target moths |
| Traps | Targeted and effective for specific moth species | Temporary solution, can be costly |
Remember, moths can be both pollinators and a nuisance in your home. Proper prevention and management will help you maintain a balanced ecosystem while protecting your belongings from damage.
Conclusion
While the vast majority of moth species are harmless and serve essential roles in ecosystems as pollinators and decomposers, a small subset can pose minor threats.
The larval stages of puss moths and spongy moths have the ability to poison a human or animal and damage crops respectively.
However, the portrayal of moths as universally hazardous is misleading.
Reader Emails
Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about moths. Scroll down to have a look at some of them.
Letter 1 – Arctiid: Empyreuma affinis
I live in Fort Myers Beach, Florida and saw this bug holding on to the ceiling of my porch one morning. I wish I had better close up’s, but was hoping you could identify it for me.
Thanks!
Spencer Bruce
Hi Spencer,
We spent considerable time in books and online searching for your moth, one of the wasp mimics.
We finally turned to Eric Eaton, and his answer is also very general: “It is an arctiid, but I don’t know which one. Pretty! Eric ” One day we hope to identify your lovely moth which might be a tropical species blown up by recent storms.
(09/08/2005) Eric Eaton came to the rescue: “Bugguide had a specimen of the same thing today, and it was identifed as: an adult of the spotted oleander caterpillar, Empyreuma affinis.
There is a website on it from the IFAS (Florida agriculture something or other:-) Eric”
Letter 2 – Bug caught on Surveilance Camera
Location: USA, Central CA, 4,000’ elev.
April 22, 2013 7:37 pm
This flying Bottlebrush is fast and acrobatic. Keeps tripping my night security camera.
I wanted to see if the lynx was coming around, but this critter keeps turning the ’record’ on the camera all night. It doesn’t seem to have any head, just a thin rod-like ’body’ with many circular rows of bristle-like ’wings’.
I turned the red LED’s off on the camera to see if that will stop him. I do have recorded video of him zipping around, if that would help.
I’ve never seen or heard about anything like this in this area; however, the insects at this elevation are quite unique to me. The photos are with infrared illumination.
Signature: Tom
Dear Tom,
We believe this is a moth or some other nocturnal insect. We also believe the slow shutter speed has captured its movement rather than accurately recording its shape.
What you are viewing is several flaps of the wings as the insect moves forward. We would suggest a net if you want a more accurate identity.
Letter 3 – Butterfly Moth from Spain
Geographic location of the bug: Alicante, Spain
Date: 05/06/2020
Time: 09:27 AM EDT
Your letter to the bugman: Hello,
I have two of these beauties flying around our garden, one male one female as they have been trying to mate the last couple of days.
Does anyone recognise them? I’ve lived in Spain 15 years and never seen them here before.
They are lovely.
Thank you
How you want your letter signed: Michaela
Dear Michaela,
This is a Butterfly Moth, Paysandisia archon, a South American species that has been introduced to Europe.
According to the Invasive Species Compendium, it: “is a Neotropical species indigenous to South America: Argentina, Brazil, Paraguay and Uruguay.
In Europe it has been reported from Bulgaria, Cyprus, Denmark, France, Italy, Greece, Slovenia, Spain and the UK.”
Letter 4 – Butterfly Moth from Spain is invasive species: Paysandisia archon
Ed. Note: June 25, 2014
This request arrived during our absence from the office, hence the delay in our response. We are still feebly trying to catch up on our unanswered mail.
Subject: Hawk(moth)
Location: calonge,Girona,Spain
June 18, 2014 6:35 am
16-06-2014 I found this moth flying at daytime in our garden.It looks like a kind of hawk-moth,but I´ve never seen this species before.
The wings are a bit worn off,but the hindwings are still very eyecatching with the bright orange color and black/white markings.Location:Calonge,Girona,Spain.
I hope somebody knows the scientific name.
Thanks!
Signature: Cheers,insectlover123
Subject: Moth
Location: calonge,girona,spain
June 22, 2014 2:04 am
A few days ago I´ve already sent two pictures of this moth.
I´m very curious what species it is.
Location: Calonge,Girona,Spain.In our garden
Date:16 june 2014 daytime
A few days later on 20 june 2014 I´ve found the same specimen in our kitchen against the window-pane.
It was not very active and clearly dying.Indeed after an half an hour it died and I put in a box.
On the picture is the prepared species.
Hope you can help!
Signature: insectlover123
Dear insectlover123,
This stunning moth is a Butterfly Moth, Paysandisia archon, and according to Karl who researched this for us several years ago:
“The species is Paysandisia archon and according to Wikipedia: ‘It is native to Uruguay and central Argentina and has been accidentally introduced to Europe, where it is spreading rapidly.
It is considered the only member of the genus Paysandisia.’ The larvae are palm borers and are considered a serious pest. The spread of this species is being closely tracked in France and several other Mediterranean countries and it is likely that someone may be interested in this sighting. “
According to Palms Journal: ” [it] has been discovered recently on the French Riviera as a new pest and appears to be very noxious to palms. It is native to Argentina and Uruguay and was probably introduced into France through the importation of mature plants of Trithrinax campestris.”
You might want to consider reporting this to your local agricultural authorities.
Dear Daniel,
Thanks for your message and information.
I´m very happy that I know which species it is now:)
Much appreciated!
I´ll consider to report this to my local agricultural authorities.
Kind regards,
Jimmy Hoffman
Letter 5 – Atteva sciodoxa???
Dear Bugman,
I suspect this is an Atteva sp. (refer attached pics). Please confirm.?Could you give the species name and also the general duration for its life cycle.
It was found infesting Eurycoma longifolia.? hope to hear from you soon. kind regards??
Norman
Hi Norman,
You have done your research nicely. We located a few matches for Atteva and Eurycoma online, but sadly, the URLs were no longer active. The specis is Atteva sciodoxa, but we couldn’t locate a photo.
One site listed the moth in Thailand. We also located some very similar looking moths in the genus from Australia. Alas, you provided us with no location information.
sorry bugman, i realised that after i sent the email. The location was in Malaysia. thanks, i also suspected it to be Atteva sciodoxa after googling it, but as you said, the sites were no longer active and I couldnt find the pics to compare. cheers
Letter 6 – Butterfly Moth from Argentina: Paysandisia archon
Location: Buenos Aires, Argentina
March 6, 2013 4:22 pm
Hello! I really love insects, especially moths. Where I live, we don’t get to see many cute or colourful moths besides the normal household ones, so I was quite shocked when I saw this little beauty roaming around my house!
I’m not sure if this moth is native to this part of the world; I think it might be an introduced species. I’d be really happy if you helped me identify this handsome little fellow.
(Sorry about the low quality pics)
Signature: Paula
Dear Paula,
We believe we have correctly identified this as a Butterfly Moth, Paysandisia archon, and it is native to Argentina and it is represented on the Butterflies and Beetles of Argentina website.
According to the Fauna of Paraguay website: “These are large, colourful and generally rare, day-flying moths with clubbed antennae – superficially resembling butterflies.
Sensilla present on the antennal clubs. Large external ocelli and chaetosemata absent. Probocis often well-developed, occasionally reduced. Maxillary palpi small, labial palpi upturned. Epiphysis present and tibial spur formula 0-2-4.
Sensory brushes occur on the pretarsus before the claws. Wings broad, venation little reduced. Wing coupling via frenulum-retinaculum system. CuP vein present or absent in both wings.
Male genitalia with characteristically curved aedagus. Females typically with elongated ovipositor. (Scoble 1995).”
Interestingly, we identified your moth very quickly in our own archive because we thought it resembled a Fruit Piercing Moth from the family Noctuidae (see Purdue University Entomology website), a mistake we made before when a photo of a Butterfly Moth was sent to us from France.
When we learned its true identity, we discovered it was accidentally introduced to Europe from South America, and since the larvae are borers in palms, it is expected to be a problematic invasive exotic species in France if it becomes widely established.
Letter 7 – Butterfly Moth from France
Subject: Butterfly moth
Location: Peyriac-Minervois, France
September 4, 2013 1:22 pm
We found in our courtyard in Peyriac-Minervois, France, what seems to be a Butterfly Moth. A second one arrived a few hours later. They were very inactive on the ground. The first one disappeared after 48 hours.
The second is barely alive after 4 days. We had the impression that the ”French” are monitoring them as they seem to be considered rare pests, although we don’t know why.
Photographs are attached. The ruler shown is in inches.
We should be very interested to know what trouble they cause.
Signature: Roger and Linda
Dear Roger and Linda,
We agree that this is the introduced Butterfly Moth, Paysandisia archon, which is native to South America.
According to the Palms.org website: “At the beginning of summer 2001, INRA (Institut National de la Recherche Agronomique) in Antibes (France) was alerted by people from the Department of Var that they had a lot of palm trees severely damaged by a “white grub,” and some palms had even died.
It was the starting point for an official report of a new exotic moth introduced accidentally into France. This beautiful insect – the largest introduced accidentally into Europe – is indeed a serious pest for a great number of palm species.”
Dear Daniel,
Thank you very much for your prompt and informative reply, which explains our moth’s lack of interest in our revival efforts, (sugar water, grapes and flowers!)
We are surrounded by vines and only a very few ornamental palms here.
Best wishes.
Roger and Linda
Letter 8 – Common Lytrosis
It was too high to get a straight on picture…..is it a moth or butterfly?? How very beautiful….the color and the texture intrigue me. I’m attaching two pictures I was able to take. Thanks in advance for help
Eileen Wanamaker
where are you located????????
Southeastern PA
Hi Eileen,
Thanks for the additional information. We are having trouble identifying your moth. We thought it might be an Owl Moth, Thysania zenobia, or possibly one of the moths in the genus Zale, but we can’t be certain.
No, it is not an Owlet Moth….I’ve checked and the pictures online look nothing like the moth I took the picture of. It seems to be a type of moth in the Zale family, the best I can compare, but I can’t find the exact name for it.
how large was it???
Ed. Note: (06/22/2008)
We contacted lepidopterist Julian Donahue and here is what he has to say: “It’s a geometrid: The Common Lytrosis, Lytrosis unitaria. Looks like a male, judging from the antennae. Julian”
Letter 9 – Copiopteryx semiramis from Ecuador
Location: Milpe Eco Lodge near Mindo Ecuador
September 12, 2010 7:38 pm
Attached are three photos of a giant moth seen August 21, 2010 at an eco lodge near Mindo, Ecuador.
The moth was photographed at night as it was perched on wood wall and seemed to be about 8 to 10 inches from top to the tip of its tails. I believe it may be largest I have ever seen.
I have named the month the Milpe Fantasma Moth since no one seems to know what it is.
Signature: Gordon McWilliams
Dear Gordon,
Thank you so much for sending us a larger digital file. The original file was only 9K and your subsequent file was 4368K, and increase of nearly 500X the resolution.
Our readership appreciates the clarity of your new image of what we believe to be a female Copiopteryx semiramis based on our identification using the World’s Largest Saturniidae Site.
The tails of the males are even longer. An image may also be found on the Moths of Belize website.
Daniel,
Thank you very much for identifying this bizarre moth. It was quite a shock when we first discovered it. I have sent your ID info to the owner of the eco lodge.
Gordon McWilliams
You’re welcome.
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