Wild Facts About The Brassy Blister Beetle
Brassy Blister Beetle Photo Gallery
Brassy Blister Beetle. Lytta aenea. Insect. Photograph taken and design created by the author. Copyright © 2025 Now I Wonder. All rights reserved.
Brassy Blister Beetle. Lytta aenea. Insect. Photograph taken and design created by the author. Copyright © 2025 Now I Wonder. All rights reserved.
Brassy Blister Beetle. Lytta aenea. Insect. Photograph taken and design created by the author. Copyright © 2025 Now I Wonder. All rights reserved.
What Do Brassy Blister Beetles Look Like?
- Adult Brassy Blister Beetles are long, soft-bodied insects that have:
- Broad heads,
- Downward-pointing mouthparts,
- Eleven-segment abdomens,
- Soft leather wing covers (called “elytra”).
- Their elytra curve around the sides of their abdomens but too short to cover the tips.
- Brassy Blister Beetles have:
- Metallic, brassy brown-green elytra that meet in a long, straight line down the center of their backs,
- These insects can look more blue, green, or brown depending on the light and viewing angle.
- Green-brown heads and pronotums (the most visible part of their thoraxes),
- Both are furred with coverings of dense, short hairs (called setae).
- Pronotum is narrower than both the head and the base of the wing coverings.
- Short, densely packed setae that extend below the sides of the elytra.
- Large, bulbous black eyes,
- Moniliform antennae made up of eleven rounded, bead-like segments (called antennomeres)
- Orange legs with black leg joints
- Metallic, brassy brown-green elytra that meet in a long, straight line down the center of their backs,
Where To Find Brassy Blister Beetles
- Brassy Blister Beetles live in the eastern United States from New England to the north, south to Georgia, and west to Missouri, Oklahoma, and Texas (Evans 2014).
- Look for adult beetles in the spring on plants in the Rose family (Rosaceae), like cherry (Prunus), hawthorn (Crataegus), and apple (Malus) (Evans 2014).
Strange Courtship: Antenna Pulling
- Like its blister beetle cousin, the Red and Black Blister Beetle (Tricrania sanguipennis), male Brassy Blister Beetles court females by tugging gently on their antennae.
- The male approaches the female from behind, grabs one of the female’s antennae with his legs, and pulls (Evans 2014).
- It’s a subtle but important part of their courtship, and a behavior that shared by only a few other beetle families.
A Bizarre Babyhood: Hypermetamorphosis
- Most insects grow through a series of similar-looking stages called “instars”, getting bigger each time they molt and shed their exoskeletons.
- But Blister Beetles develop differently and go through something called “hypermetamorphosis”.
- During hypermetamorphosis, the larvae change shape dramatically as they grow.
- The first stage is called a “triungulin”—each larva is tiny, active, and mobile with long legs.
- Triungulins crawl around in search of a host; in the case of Brassy Blister Beetles, the larval hosts are probably bees.
- Once the triungulins find hosts, they molt in a slower, legless form and begin to feed on their hosts’ bodies.
- Over time, the beetle larvae change again into grubs that have small legs and eventually pupate into adult beetles.
A Blister Beetle’s Potent Defense: Cantharidin
- Like all species in family Meloidae, Brassy Blister Beetles pack a powerful defense against predators.
- These beetles contain cantharidin, a caustic chemical that causes severe blisters on skin, eyes, and mucous membranes, like mouths.
- When threatened, Brassy Blister Beetles ooze cantharidin-filled fluid from their leg joints.
- Called “reflex bleeding”, blister beetles share this defense strategy with several other beetle species in other families, including Ladybugs and Big Dipper Fireflies (Photinus pyralis).
- However, the fluid that these other beetle families exude is noxious and bad-tasting but not necessarily harmful to predators.
- The fluid that Blister Beetles exude is directly caustic and actually injures tissues to which it contacts.
- When threatened, Brassy Blister Beetles ooze cantharidin-filled fluid from their leg joints.
- Cantharidin makes blister beetles taste terrible and injures many types of predators who are unwise enough to attack them.
- Even otherwise opportunistic predators like Common Raccoons (Procyon lotor) learn to avoid blister beetles (Carrel 1999, https://doi.org/10.1023/A:1020970624529).
But Nobody’s Perfect
- Unfortunately for Brassy Blister Beetles, even such a potent chemical defense like cantharidin isn’t enough to stop some predators.
- Several predators have evolved the ability to circumvent or withstand the blistering effects of cantharidin and prey on blister beetles. These include:
- Robber flies (family Asilidae),
- Mantids, such as the Chinese Mantis (Tenodera sinensis) and the Carolina Mantis (Stagmomantis carolina),
- Eastern Meadowlarks (Sturnella magna),
- Eastern Bluebirds (Sialia sialis),
- Southern House Spiders (Kukucania hibernalis) (Carrel 1999, https://doi.org/10.1023/A:1020970624529).
- Some other insects even steal the blister beetles’ cantharidin for their own purposes.
- Beetles in family Anthicidae (Antlike Flower Beetles) scavenge dead blister beetles to collect cantharidin for themselves.
- Males pass the caustic chemical to females during mating,
- Females then use it to protect their eggs and larvae (Evans 2014).
My Nature Journal Sightings
03/28/2025 Nature Journal
Imagine my surprise when I stepped out my back door and came face to “face” with this rather intimidating guy.
I could tell immediately it was a beetle of some sort, since its wing covers looked fairly hard and met in a straight line down the insect’s center back, and the antennae it waved in my direction were bead-like.
I never touch any wild creature while out on my nature walks but definitely wouldn’t have touched this guy, even if keeping one’s distance isn’t both best practice for safety, as well as kind.
Most of the time, bright colors on insects represent a visual warning that they are best left alone, either because they are toxic, dangerous, or simply want you to think they are.
This beetle’s bright orange legs warned me that discretion was definitely the better part of valor, even if I didn’t yet know why.
It wasn’t until I could look this beetle up in my reference field guide that I realized my instinct was correct. The cantharidin that blister beetles release when threatened can blister human skin.
And that would be a high price to pay when all I wanted to do was fill my bird feeder.
Conditions
|
Temperature |
55° F / 13° C |
|
Weather |
Passing clouds |
|
Humidity |
20% |
|
Time Of Day |
1:52 PM |
|
Setting |
Suburban backyard |
Scientific Classification
|
Kingdom |
Animalia (animals) |
|
Phylum |
Arthropoda (arthropods) |
|
Class |
Insecta (insects) |
|
Order |
Coleoptera (beetles) |
|
Family |
Meloidae (blister beetles) |
|
Genus |
Lytta |
|
Species |
L. aenea |
Scientific Name |
Lytta aenea |
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