Anyone searching for the different types of beetles in Colorado will quickly discover a surprisingly large cast of characters, from wood-boring pests threatening ash trees to gentle, fuzzy pollinators drifting over wildflowers on the plains. Colorado is home to more than 850 documented beetle species, and counting, which makes this state one of the richer beetle habitats in North America once you account for its mix of prairie, foothill, and alpine ecosystems.
This guide narrows that huge list down to 11 beetles that residents and visitors are most likely to actually encounter, whether in a garden, along a riverbank, or on a hiking trail. Each entry below covers identification features, habitat preferences, and the role each species plays in Colorado’s ecosystems. For readers curious about how this diversity compares elsewhere, it’s worth checking out how how many beetle species exist worldwide or exploring the broader range of insect diversity found across different habitats.
Pro Tip: Most beetles are easiest to identify by three features together: body shape and size, wing cover (elytra) pattern or color, and the plant or habitat where you found them. Relying on color alone often leads to misidentification, since many unrelated species share similar shades of black, brown, or metallic green.
Ten-lined June Beetle
The ten-lined June beetle (Polyphylla decemlineata) is one of the largest and most recognizable scarab beetles a person can find in Colorado. Adults and the related Polyphylla species are the largest scarab beetles in Colorado, ranging from 22-30 mm in length. Its common name comes from the pale stripes running down its wing covers, and males carry large, fan-shaped antennae they use to detect females.
This species has an unusual defense trick: it can make a hissing sound when touched or otherwise disturbed, which can resemble the hissing of a bat, produced by their wings pushing down and forcing air out between their wings and back. The ten-lined June beetle is widely distributed across Colorado, most commonly found east of the Rockies including the San Luis Valley, and it tends to favor lighter, sandier soils. Adults of this beetle usually fly from late June through early August, which is when most sightings occur, often around porch lights or streetlamps at night.
The larvae are thick, white grubs that live underground for several years feeding on plant roots, occasionally causing damage to turf and orchard crops. Readers who want to compare how this species fits into scarab diversity elsewhere might find the beetle roster in Kansas beetle populations useful, since Polyphylla species also range across the Great Plains. More background on this beetle’s classification and range is available from Colorado State University’s High Plains IPM guide.
Emerald Ash Borer Beetle
The emerald ash borer (Agrilus planipennis) is not a species anyone should be excited to see, since it ranks among the most destructive invasive insects ever introduced to North America. This wood-boring beetle is native to Asia and was introduced into North America during the 1990s, likely via shipping materials such as ash wood pallets. Since then it has reshaped urban forestry across much of the continent.
Identification relies on its slender, metallic build: typical specimens show a bright, metallic, emerald green color overall, with the elytra usually appearing somewhat duller and slightly darker green. At roughly 9 to 13 mm long, it’s actually the smallest beetle on this list, which can make it tricky to spot until the damage to a tree’s canopy becomes obvious.
This beetle was first detected in Colorado in Boulder in September 2013, and it has continued spreading since. In June 2023, researchers from Colorado State University confirmed its presence in two additional towns, Carbondale and Littleton. The stakes for Colorado’s urban canopy are significant: approximately 15% of the trees in Colorado’s urban forests are ash, making this insect a major threat to urban forests statewide.
Homeowners in states with established EAB populations, including the heavily affected forests described in guides to Ohio’s insect populations, have dealt with similar tree losses for over a decade. For monitoring maps and treatment guidance, the Colorado State Forest Service’s EAB resource and Colorado Parks and Wildlife’s species profile are both worth reviewing.
Important Note: The emerald ash borer is frequently confused with native lookalikes. Homeowners who suspect an infestation should confirm identification with a local extension office before removing healthy trees.
Checkered Melon Beetle
The checkered melon beetle (Diabrotica spp.) is a small leaf beetle that gardeners in the southeastern part of the state are most likely to run into. This insect is a common sight in southeastern Colorado, showing a black and white pattern on its back, and growing to about 7 mm long. That compact size and bold contrast make it fairly easy to pick out among foliage once you know what to look for.
As its name suggests, this beetle has a strong preference for cucurbit crops, feeding on the leaves and sometimes the fruit rind of melons, squash, and related plants. Populations tend to build through the growing season, and heavy feeding pressure can stunt young vine crops if left unmanaged. Gardeners dealing with similar leaf beetle pests in other regions can compare notes with growers featured in guides to New Jersey beetle species, where cucumber beetle relatives cause comparable garden damage. Additional Colorado beetle profiles, including this species, are cataloged by Wildlife Informer’s regional beetle guide.
Flower Longhorn Beetle
Flower longhorn beetles are a group within the family Cerambycidae, and in Colorado the most frequently recorded members belong to the genus Typocerus spp., along with related species once classified under the older genus name Strangalia. Records for Colorado list several forms, including S. emarginata, S. luteicornis, and multiple Typocerus species. All share the elongated, narrow-bodied look and long antennae typical of longhorn beetles.
Unlike many of their wood-boring cousins, flower longhorns spend their adult lives visiting blossoms rather than burrowing into trees. They feed on pollen and nectar, often perching in the open on daisies, yarrow, or other flat-topped flower clusters where they’re easy to photograph. Their larvae, by contrast, typically develop inside dead or decaying wood, giving this group a life cycle split between two very different worlds.
Anyone comparing longhorn diversity across states may enjoy the beetle roundup for New York’s beetle fauna, where several related Cerambycidae also turn up on summer wildflowers. A broader state-by-state beetle index, including flower longhorn records, is maintained by BeetleIdentification.org’s Colorado listing.
Dung Beetle
Dung beetles occupy one of the more underappreciated ecological roles among Colorado’s beetles, and Colorado’s records point to the genus Dichotomius sp. as a regularly documented representative. This genus appears directly in state insect databases, confirming that true dung-feeding scarabs are part of Colorado’s beetle community rather than just a rangeland curiosity.
These beetles locate fresh manure using scent, then either roll a portion away, bury it directly beneath the pile, or tunnel into it to lay eggs, depending on the species and its particular strategy. That process recycles nutrients back into the soil, reduces fly breeding sites, and speeds up the breakdown of waste on rangeland and pasture.
Dung beetles reach far greater diversity in warmer climates, and readers curious about that contrast can look at the astonishing variety cataloged in guides to Amazon rainforest insect life, where dozens of dung beetle species coexist in a single patch of forest.
Key Insight: A single healthy dung beetle population can bury manure fast enough to noticeably cut down fly populations on pastureland, which is one reason ranchers often consider them beneficial rather than pests.
May Beetle
May beetles belong to the genus Phyllophaga spp., with Colorado records specifically noting Phyllophaga lanceolata among the state’s documented species. These stout, brown-to-black scarabs are close relatives of the ten-lined June beetle covered earlier, and the two groups are frequently mixed up by casual observers.
The overlap makes sense biologically: May and June beetles in the genus Phyllophaga share a similar life history, with soil-dwelling white-grub larvae that feed on plant roots, while adults are often nocturnal, seasonally abundant in late spring and summer, and commonly attracted to lights. The larval stage, often called a white grub, can spend one to three years underground before emerging as an adult, which explains why lawn damage from these grubs sometimes appears in cycles rather than every single year.
Common Mistake: Many people call every brown beetle drawn to a porch light a “June bug,” but that label actually covers several distinct species across at least two genera, Phyllophaga and Polyphylla, each with different size ranges and habits.
Gardeners in other beetle-rich states face similar white grub concerns, as detailed in resources covering Minnesota’s beetle species, where related Phyllophaga populations also affect turf and crops.
Predaceous Diving Beetle
Predaceous diving beetles bring an entirely different lifestyle to this list, since they spend most of their lives underwater. Colorado’s state beetle records include the species Acilius mediatus, part of the family Dytiscidae, a group built for swimming rather than crawling or flying.
Their bodies are smooth, oval, and streamlined, with flattened hind legs fringed with hairs that work almost like paddles to propel them through ponds and slow streams. Adults are active predators, hunting mosquito larvae, small tadpoles, and other aquatic invertebrates, while also occasionally surfacing to trap a bubble of air beneath their wing covers for breathing underwater.
This dual air-and-water lifestyle makes them one of the more specialized beetle families found in the state’s wetlands and irrigation ditches. Similar aquatic beetle communities show up across the northern half of the continent, including the species highlighted in overviews of insects found throughout Canada, where Dytiscidae diversity is also well documented.
Black Blister Beetle
The black blister beetle (Epicauta pensylvanica) is a soft-bodied, all-black insect that shows up reliably on late-summer wildflowers across the state. This species can grow up to 12 mm long, is common in Colorado, and is usually seen feeding on the nectar and pollen of flowers, with a particular attraction to bright yellow blooms such as goldenrod and rabbitbrush.
Its life cycle has an unusual twist for a plant-feeding adult: adults lay their eggs in the soil where the larvae hatch and live, and the black blister beetle larvae actually eat grasshopper eggs before overwintering and pupating, with new adults emerging over the course of the following summer. That grasshopper-egg diet makes the larval stage genuinely beneficial for controlling rangeland pests, even though the adult can be a mild nuisance around flower beds.
Important Note: Blister beetles, including this species, secrete a defensive compound called cantharidin that can cause skin irritation if the insect is crushed against bare skin. It is best to avoid handling them directly, and livestock owners should be aware that dried blister beetles baled into hay can be toxic to horses.
Readers wanting to distinguish this species from other dark-colored beetles can check the comparison guide on common black beetle species, while anyone concerned about insect bites and stings more broadly may find the overview of biting and stinging insects helpful for context.
Burying Beetle
Burying beetles, genus Nicrophorus spp., belong to the carrion beetle family Silphidae and are recognized as a distinct group within Colorado’s documented insect fauna. These beetles are usually black with bold orange or red markings across their wing covers, giving them a strikingly bright appearance for an insect that spends its life around dead animals.
Their behavior is genuinely remarkable among beetles: a mated pair locates a small dead animal, such as a mouse or songbird, buries it underground, and then strips off fur or feathers before shaping the carcass into a ball that serves as a food store for their larvae. Both parents typically stay to guard and feed the developing young, a level of parental care that is rare among insects and has made this genus a favorite subject for behavioral researchers.
This recycling role parallels the pattern seen in dung beetles, both groups converting waste that would otherwise attract flies and bacteria into a resource that benefits the wider ecosystem. Similar carrion beetle diversity appears in guides to Maryland’s beetle populations, where Nicrophorus species are also well represented.
Bumble Flower Beetle
The bumble flower beetle (Euphoria inda) earns its name honestly, since its rounded, fuzzy body and buzzing flight pattern make it an easy beetle to mistake for an actual bumble bee at first glance. It belongs to the scarab subfamily Cetoniinae, commonly called flower chafers, a group known for visiting blossoms and ripening fruit rather than chewing on roots or wood.
Adults are covered in fine golden-brown hair over a mottled tan-and-black body, and they’re most active on warm days in late summer and early fall, when they can often be found clustered around overripe fruit, sap, or open flowers.
Their larvae live in decaying organic matter, compost, and leaf litter, feeding on decomposing plant material rather than living roots, which makes them largely harmless to garden plants despite their intimidating buzz. Because the resemblance to actual bees is so strong, this species often gets misreported in citizen sightings; readers curious about the real pollinators sharing its habitat can compare notes with the species covered in guides to Colorado’s native bee species.
Apple Flea Beetle
The apple flea beetle, genus Altica spp., closes out this list as one of the smaller but more agile species a gardener might encounter. Like other members of the flea beetle group within the leaf beetle family Chrysomelidae, it has noticeably enlarged hind femora that let it spring away instantly when disturbed, a defense mechanism that gives the whole group its common name.
Adults are typically small, shiny, and metallic blue-green to black, and they feed by chewing small, rounded holes or shallow pits into the leaves of apple trees and related plants in the rose family. Heavy feeding can leave foliage looking lacy or skeletonized, though established trees usually tolerate moderate damage without lasting harm. Larvae feed on the same host foliage before dropping to the soil to pupate, completing a life cycle that can produce more than one generation per growing season in warmer parts of the state.
This species is documented among Colorado’s noteworthy insects by state agricultural extension resources tracked in the InsectIdentification.org Colorado beetle database. For readers who enjoy observing small leaf beetles up close, the overview of insects commonly kept as pets offers a lighter look at how people interact with beetles beyond pest management.
Quick Reference: Comparing Colorado’s Common Beetles
| Common Name | Typical Size | Peak Activity | Key Identifying Trait |
|---|---|---|---|
| Ten-lined June Beetle | 22-30 mm | Late June-early August | Pale wing stripes, hisses when disturbed |
| Emerald Ash Borer | 9-13 mm | Late spring-summer | Metallic emerald green body |
| Checkered Melon Beetle | ~7 mm | Growing season | Black and white checkered pattern |
| Flower Longhorn Beetle | Varies by species | Summer | Long antennae, found on flat flower clusters |
| Dung Beetle | Varies by species | Warm months | Found near manure, digs or rolls dung |
| May Beetle | Medium, stout | Late spring | Brown, drawn to lights |
| Predaceous Diving Beetle | Small-medium | Warm months, aquatic | Smooth oval body, paddle-like legs |
| Black Blister Beetle | Up to 12 mm | Late summer | All-black, soft-bodied, on yellow flowers |
| Burying Beetle | Medium-large | Warm months | Black with orange/red markings |
| Bumble Flower Beetle | Medium, rounded | Late summer-fall | Fuzzy, bee-like buzzing flight |
| Apple Flea Beetle | Small | Growing season | Metallic blue-green, jumps when touched |
Taken together, these 11 species show just how varied Colorado’s beetle life really is, spanning wood-boring pests, aquatic predators, pollinators, and nature’s own cleanup crew. Some, like the emerald ash borer, warrant real concern and active monitoring, while others, like the bumble flower beetle or flower longhorn beetle, are simply fascinating to watch on a summer afternoon.
For a broader look at how Colorado’s insect life compares to other regions, guides covering Missouri’s beetle diversity and Texas insect populations offer useful points of comparison for anyone building a wider picture of North American beetle diversity.