# Bean Leaf Beetle (*cerotoma trifurcata*)

The Bean Leaf Beetle (Cerotoma trifurcata) is a common and highly adaptable agricultural beetle found across North America. Belonging to the leaf beetle family Chrysomelidae, this small insect plays a major role in local ecosystems and crop environments. While often recognized as a pest due to its fondness for soybeans and other legumes, the beetle showcases incredibly interesting biological variations, including diverse color morphs that can range from yellow to red with varying spot patterns. In the spring, they emerge from forest margins to colonize young host plants, where they feed on leaves and pods. Despite their agricultural impact, they are an essential food source for many native birds, spiders, and predatory insects. Their life cycle relies on leguminous plants, where adults feed on foliage while their larvae live underground, consuming roots and nitrogen-fixing nodules. This dual-habitat lifestyle highlights their specialization and complex interaction with their environment.

- **Category:** [Insects](https://www.snappit.app/explore/categories/insect)
- **Rarity:** Common
- **Danger:** 1/5 · Very low
- **Snaps:** 1
- **Habitat:** Typically found in agricultural fields, pastures, gardens, and grassy borders where leguminous plants are grown.

![Bean Leaf Beetle](https://inaturalist-open-data.s3.amazonaws.com/photos/158272170/medium.jpg)

Photo: Andrew Sebastian, CC BY 4.0 · [iNaturalist](https://www.inaturalist.org/photos/158272170)

## Appearance

The Bean Leaf Beetle is a small, oval-shaped insect measuring approximately 0.3 to 0.6 centimeters in length. Its color is highly variable, ranging from light yellow and tan to vibrant red. The most reliable identifier is a distinct black, backward-pointing triangle located at the front margin of the wing covers, right behind the black head. Most individuals also display four prominent rectangular black spots on their back, bordered by a thin black band along the outer edges of the wing cases, although some individuals may lack spots entirely.

## Taxonomy

- **Kingdom:** Animalia
- **Phylum:** Arthropoda
- **Class:** Insecta
- **Order:** Coleoptera
- **Family:** Chrysomelidae
- **Genus:** Cerotoma

## Interesting facts

- Bean Leaf Beetles overwinter as adults in leaf litter and can survive freezing temperatures by producing glycerol, a natural antifreeze.
- Their color variation is so dramatic that early entomologists mistakenly classified different color morphs of this single species as entirely separate species.
- They are major vectors for plant diseases, transmitting the devastating Bean Pod Mottle Virus through their saliva as they feed.

## Special abilities

- **Thanatosis:** When threatened, this beetle will immediately drop from foliage and play dead, blending into the soil below to escape predators.
- **High Color Polymorphism:** This species exhibits extreme genetic variation in coloration, allowing individuals to appear red, yellow, or orange, which helps confuse predatory search images.
- **Nodule Excavation:** In their larval stage, they can burrow directly into the underground nitrogen-fixing root nodules of legume plants, exploiting a specialized subterranean food source.

## Measurements & details

- **Length:** 0+ cm
- **Wingspan:** 1+ cm
- **Weight:** 0.00001+ kg
- **Lifespan:** 0+ years
- **Clutch Size:** 100+
- **Incubation:** 5+ days

## Diet & Feeding

Both larvae and adults feed exclusively on leguminous plants, targeting roots underground and foliage aboveground.

- **Age differences:** Larvae feed underground on roots and nitrogen-fixing nodules, whereas adults feed aboveground on leaves, flowers, and bean pods.
- **Primary Foods:** Soybean leaves, Green bean pods, Alfalfa leaves, Clover, Wild legume roots
- **Foraging Method:** Grazing

## Ecological connections

- **Host plant:** [Soybean](https://www.snappit.app/explore/soybean) (*Glycine max*) — Adults feed on the leaves and pods, while larvae consume the roots and nitrogen-fixing nodules.
- **Eaten by:** Spined Soldier Bug (*Podisus maculiventris*) — A generalist predatory stink bug that preys on both adult and larval bean leaf beetles.
- **Parasite:** Tachinid Fly (*Celatoria diabroticae*) — A parasitoid fly that deposits eggs on the beetle, with the developing larvae eventually killing the host.

## Safety

**Danger:** 1/5 · Very low

No special safety notes yet.

## Frequently Asked Questions

### How to identify Bean Leaf Beetle?

Look for hard wing covers meeting in a line down the back, then compare the antennae, body shape, legs and markings. Metallic colors shift a lot with lighting. Beetle Identifier: upload a photo and compare the visible details.

### How long is Bean Leaf Beetle?

0+ cm

### What is Bean Leaf Beetle's wingspan?

1+ cm

### How much does Bean Leaf Beetle weigh?

0.00001+ kg

### How long does Bean Leaf Beetle live?

0+ years

### What does Bean Leaf Beetle eat?

Both larvae and adults feed exclusively on leguminous plants, targeting roots underground and foliage aboveground.

### Where is Bean Leaf Beetle usually found?

Typically found in agricultural fields, pastures, gardens, and grassy borders where leguminous plants are grown.

### How does Bean Leaf Beetle hunt?

Grazing

## Where to spot

- [Circleville Historic District](https://www.snappit.app/guides/places/circleville-historic-district) — Ohio, US · Historic District
- [J. Edward Roush Lake](https://www.snappit.app/guides/places/j-edward-roush-lake) — Indiana, US · Natural Landmark

## More Insects

- [Common Eastern Bumble Bee](https://www.snappit.app/explore/common-eastern-bumble-bee) (*Bombus impatiens*)
- [Spotted Lanternfly](https://www.snappit.app/explore/spotted-lanternfly) (*Lycorma delicatula*)
- [Brown-belted Bumble Bee](https://www.snappit.app/explore/brown-belted-bumble-bee) (*Bombus griseocollis*)
- [Eastern Carpenter Bee](https://www.snappit.app/explore/eastern-carpenter-bee) (*Xylocopa virginica*)

---

Source: [Bean Leaf Beetle: Facts & Places to See — Snappit](https://www.snappit.app/explore/bean-leaf-beetle)