Thousands of insect species live in Colorado!

Trying to list them all would be impossible. So below, you will find the most common and abundant bugs that live in Colorado. I did my best to find an array of different types, such as bees, beetles, flies, mantises, ants, etc.

Also, this article ONLY lists INSECTS. Please check out these other ID guides if you are searching for something else:

SPIDERS / SCORPIONS / TICKS / MILLIPEDES & CENTIPEDES

18 Common Insects in Colorado:

#1. Common Green Bottle Fly

Lucilia sericata

Adults have metallic blue-green or copper-green bodies.
They have black hair on their backs, black legs, and antennae. Transparent wings with light brown veins.
They’re slightly larger than houseflies.

The Common Green Bottle Fly is one of the most common and well-known insects in Colorado.

These bugs are not many people’s favorite, but they have some critical jobs in forensic, veterinary, and medical science! Their larvae or maggot stage can help scientists determine the time of death in investigations.

In their natural habitat, Green Bottle Flies are essential aids in decomposition, feeding on carrion and feces.

Surprisingly, they’re also pollinators. Some plants, like the Pawpaw (Asimina triloba), have adapted to attract them with flowers that have the color of drying blood and an odor of rotting meat.

These flies are incredibly prolific. A single female fly may produce 2,000 to 3,000 eggs in her lifetime. They reproduce quickly, too, completing their lifecycle in just 2 to 3 weeks.

#2. European/Western Honey Bee

Apis mellifera

They are primarily red or brown with black bands and orange-yellow rings on their abdomens.
They have hairy thoraxes and slightly hairy abdomens.

The Western Honey Bee is one of the most common insects in Colorado.

Unlike most bee species, Western Honey Bees form perennial colonies which survive for years. These colonies comprise about 30,000 to 80,000 bees, most of which are female, including the queen and worker bees.

Defending the hive can cost these bees their lives. When a Western Honeybee stings, usually its barbed stinger becomes lodged in its target. The attached venom sac and musculature are pulled from the bee, resulting in the bee’s death.

Foraging is hard work! A single worker bee flies at about 15 miles per hour and usually visits 50 to 100 flowers in a single trip.

Despite all this effort, the average worker only produces about 1.5 teaspoons of honey in her lifetime.

This honey is tasty for humans but is also essential for the hive. Workers feed honey to the larvae and feed on it themselves during the winter in temperate climates.

#3. Monarch

Danaus plexippus

Monarch butterflies have a wingspan of roughly 4 inches (10 cm).
Their recognizable coloring is a “stained glass” pattern of orange with black veins. White dots line the outside edge of the wings.
Caterpillars are plump, with black, white, and yellow bands and tentacles on each end of its body.

Monarchs are easily one of the most recognized insects in Colorado!

They are famous for their color pattern and migration. Look for Monarchs anywhere there is milkweed, which is the only food the caterpillars eat.

Most people are familiar with the declining population of Monarchs. Planting milkweed and other native flowering plants is the best way to help them.

Interestingly, Monarchs are toxic to most animals and at the very least, taste bad! This poison comes from the caterpillar’s diet, which is almost entirely made up of milkweed. Toxins from the milkweed plant stay in them, producing a bitter taste and poisonous effects.

During migration, usually in mid-September, you may even see groups of hundreds flying south!

#4. Seven-Spotted Ladybug

Coccinella septempunctata

They have red bodies with six black spots and one big black mark on the middle of their wings (hence their name).
The head is black with two white dots.
They are also known as Seven-spotted Ladybird and C-7.

When you think of ladybugs, you probably picture something similar to the Seven-spotted Ladybug!

Almost everyone loves them because of the MASSIVE amounts of aphids they eat. This makes them very useful in controlling the pest population of aphids in grasslands and farms.

Surprisingly, this insect is NOT native to Colorado.

They were introduced here from Europe as a biological control against aphids. Interestingly, while they are thriving in North America, Seven-spotted Ladybugs are declining in their native ranges in Europe.

Check out this video of the Seven-spotted Ladybug, as it is an eating machine!

#5. Asian Lady Beetle

Harmonia axyridis

Also known as the Multicoloured Asian Ladybug, Harlequin Ladybird, and Japanese Ladybug.

Adults have domed bodies and are usually about .25 inches (.6 cm) long.
Their coloration may range from yellowish-orange to red or black with variable black, orange, or red spots and markings.

The Asian Lady Beetle is NOT a true ladybug. It is similar in how it looks but not in how it acts. It is native to eastern Asia and was brought over to help control aphids like other ladybugs.

Once introduced, this species spread quickly through North America. Many people call it the “Halloween Beetle,” as it often invades homes in Colorado during October to overwinter. I know we get MANY Asian Lady Beetles coming into our house each year when the weather turns colder!

This species is considered one of the world’s most invasive insects. Their bodily fluids have an unpleasant odor and can stain fabric, so try not to crush this beetle if you find it inside!

The easiest way to identify this beetle is by the black markings on its head that look like the letters “W” or “M.”

Check out this video of how big of a problem the Asian Lady Beetle can be before winter.

#6. Common Green Darner

Anax junius

Adults grow up to 3 inches (7.6 cm) long.
Both sexes have unmarked green thoraces, bull’s eye marks on their faces, and clear wings that often become amber-tinted with age.
Males have bluish-purple abdomens with a black stripe down the middle.
Females may appear like males or have reddish-brown abdomens.

Green Darners are common flying insects in Colorado.

Named for their resemblance to darning needles, these dragonflies are nearly impossible to miss! They’re also one of the largest dragonfly species alive today.

Unlike many dragonflies, some populations of Common Green Darners migrate. Particularly in winter, they travel as far south as Panama. They’re common summertime residents of the northern US and southern Canada, and occasionally, vagrant individuals are spotted well outside their normal range.

They’ve been known to show up as far away as Japan, Russia, Bermuda, France, and the UK! Researchers suspect these are individuals who were blown off course during storms.

When researchers equipped Common Green Darners with micro radio transmitters, they found that these big dragonflies traveled about 10 miles per hour (16 kph) and up to 87 miles (140 km) per day!

#7. Bald-faced Hornet

Dolichovespula maculata

Also called the Bald-faced Aerial Yellowjacket, Bald-faced Wasp, Bald Hornet, White-faced Hornet, Blackjacket, White-tailed Hornet, Spruce Wasp, and Bull Wasp.

They have black bodies with ivory markings on their faces, legs, thoraxes, and abdomens.
Look for three white stripes at the ends of their bodies.

Bald-faced Hornets are named for the ivory markings on their face. Despite the name, these insects aren’t true hornets. They’re actually a type of yellow jacket.

These intimidating bugs don’t have a pleasant reputation in Colorado.

They aggressively defend their nests and can sting repeatedly. But while their appearance and nests can be scary, they’re pretty handy to have around (as long as the nest isn’t close to human habitation).

First, the adults feed on nectar and help to pollinate flowers. In addition, they also kill and eat other types of yellowjackets! Sometimes, in early summer, a nest will be so full of yellowjacket remains that it will have a yellowish cast! Unless their nest is somewhere you’ll come into contact with it, it’s best to leave them be.

I’m sure you have spotted one of their nests before. They are large, papery, and football-shaped. The queen builds these nests by chewing wood material and mixing it with her saliva to make a paste.

#8. Brown-belted Bumble Bee

Bombus griseocollis

They have short, even hair.
A primarily yellow thorax with a black patch between the wing bases.
Their first abdominal segment is entirely yellow, and workers usually have a brown or reddish patch in a crescent shape on the second segment.

Brown-belted Bumble Bees are incredibly adaptable. They feed on various flowers like clovers, echinaceas, goldenrods, milkweeds, and vetches. And they have a wide range of habitats in Colorado, including wetlands, agricultural areas, meadows, and even cities!

Brown-belted Bumble Bees live in small colonies of about 50 or fewer individuals. They nest underground or on the surface in organic matter.

These groups may be small, but they are mighty and will aggressively defend their nests from predators and parasites.

Unlike most bees, males are involved in raising the young. They will help incubate pupae by wrapping their legs around the cocoon and pumping their abdomens.

#9. Convergent Lady Beetle

Hippodamia convergens

Oval, dark orange body with as many as 13 black spots that vary in size.
The head is black with two white spots.

This species is a common native insect in Colorado.

Convergent Lady Beetles live in a wide variety of habitats. Look for this pretty species in your yard or garden. Unfortunately, in certain areas, they are being outcompeted and replaced by the invasive Asian Ladybeetle.

Convergent Lady Beetle Range Map

Both adults and larvae feed on aphids, but adults also eat whiteflies, insects, pollen, and other plant materials.

During colder weather, Convergent Lady Beetles form large groups called aggregations. They do this to mate and stay warm during hibernation!

When these ladybugs are in their large groups, they are collected and sold in garden centers as a source of pest control. However, they usually fly away once the person purchases and releases them. Hopefully, they put a buyer-beware notice on the container! : )

#10. Differential Grasshopper

Melanoplus differentialis

Adults are usually shiny and yellow-brown.
They have brownish-yellow or brownish-red antennae and brown eyes with light spots.
Their upper hind legs are yellow with a black herringbone pattern, and their lower hind legs are yellow with black spines.

You may remember Differential Grasshoppers from hot summer childhood days playing outside. They are one of the classic insects of summer.

The best places to find these bugs in Colorado are grasslands, but they will also inhabit vacant lots, open woodlands, roadsides, and croplands.

Their broad appetite helps them adapt to different areas. These grasshoppers feed on grasses, forbs, fruit trees, and crops.

If you’ve ever tried to catch one, you’ve probably noticed that Differential Grasshoppers are talented fliers. They can travel 10 to 100 yards in a single flight!

#11. Red-legged Grasshopper

Melanoplus femurrubrum

Adults typically range from 0.67 to 1.2 inches (1.7 to 3 cm) long.
They are variable in color and may be reddish-brown, yellow, dark brown, green, or olive green, with bright red or yellowish hindlegs featuring a black herringbone pattern.
Their wings typically extend beyond the tip of their abdomen.

You may have spotted these insects in Colorado flying away as you walk through open habitats like yards, croplands, open floodplains, vacant lots, meadows, and prairies. When startled, they can fly distances of 40 feet (12.2 m)!

These grasshoppers have to be quick to stay alive. They’re an important food source for wildlife like turkeys and quail.

Red-legged Grasshoppers feed on various grasses and other plants, including goldenrod, dandelion, clover, and vetch. But interestingly, when food is scarce, Red-legged Grasshoppers develop longer wings, allowing them to fly longer distances to new areas searching for food.

#12. Fork-tailed Bush Katydid

Scudderia furcata

Adults usually range from 1.5 to 1.75 inches (3.8 to 4.4 cm) long.
They are leafy-green with long green antennae but may have pinkish, brownish, or rusty tinges, especially in autumn.
Females have a brownish or purplish ovipositor, a sword-like appendage at the tip of their abdomen.

These insects are one of the classic sounds of the night in Colorado.

Fork-tailed Bush Katydids are one of about 250 species of katydids or “bush crickets” found in North America. Unlike true grasshoppers, they spend most of their time in trees and shrubs and rarely descend to the ground.

These bright green insects are nocturnal. They spend their nights feeding on the flowers, foliage, and fruit of the trees and shrubs they call home. Don’t worry, gardeners; they rarely cause significant damage.

Katydids can be incredibly hard to spot because they blend in perfectly with the leaves. If you get lucky, you may spot one on a tree trunk that stands out against the drab bark or around an outdoor light at night.

If you find a katydid, you should handle them with care. While not aggressive, they can give a good pinch if handled roughly.

#13. Two-striped Grasshopper

Melanoplus bivittatus

Adults are typically 1.2 to 2 inches (3 to 5 cm) long.
They are usually green or tan, with two pale yellow stripes running along the top of their bodies from above their eyes to the hind tips of their wings.
They have green or buff hind tibia with black spines.

These insects are well adapted to various habitats in Colorado!

Part of the reason they can call so many areas home is their diet. Two-striped Grasshoppers aren’t picky and will feed on grasses, herbaceous plants, woody plants, seed pods, flowers, and crops.

When food is scarce, Two-striped Grasshoppers will also scavenge on dead plants and animals. In addition, they occasionally resort to cannibalism!

These grasshoppers can be a lot of fun to find and catch. However, many insect lovers have found out the hard way that Two-striped Grasshoppers are quick to bite when handled. 🙂

#14. Boxelder Bug

Boisea trivittata

Adults are relatively flat and elongate.
They are black or dark brown with reddish lines on the edges of their forewings, margins of their abdominal segments, and the center of their pronotum (plate-like structure behind their heads).
Their eyes are red.

Boxelder Bugs are native insects in Colorado.

As their name suggests, it’s common to find them on Boxelder trees, though they will also use Maple and Ash trees. These trees are the bug’s primary food source, and they feed on the leaves, flowers, twigs, and seeds.

You may spot some of them near your house during the fall. Groups of Box Elder Bugs seek out dry, sheltered locations to hibernate through the winter.

Box Elder Bugs sometimes fall prey to birds, spiders, rodents, and praying mantises, but they have developed unique techniques to stay safe. Their red markings and foul smells they release help ward off predators.

#15. Western Conifer Seed Bug

Leptoglossus occidentalis

Adults are reddish to dark brown.
The membranous portions of their wings are dark brown and form a diamond at their rear.
Their abdomens have a yellow or orange and black pattern, but only the edges are visible until they’re in flight.

As their name suggests, Western Conifer Seed Bugs feed on the sap in conifer seeds. You can find them on a number of host plants, such as Douglas-fir, Eastern White Pine, Eastern Hemlock, Ponderosa Pine, and White Spruce.

While these insects don’t pose a considerable threat to native forests in Colorado, they can be destructive in conifer seed orchards. They’ve been known to damage up to 80% of a seed crop.

If you’re looking for Western Conifer Seed Bugs, you may hear these bugs before you spot them. They produce a loud buzzing noise in flight. It’s thought that this buzzing noise, along with their brightly colored abdomens, may mimic bees, protecting them from birds.

#16. Spruce Bug

Monochamus scutellatus

Monochamus scutellatus. (2023, October 16). In Wikipedia.

Adults are large-bodied and black with a white spot at the base of their wings.
Females may have white mottling on their wing covers.
They have strong mandibles, robust legs, a spine on each side of their prothorax, and very long antennae that may be twice their body length in males.

Also called White-spotted Sawyers, you’ll find these bugs living in Colorado in coniferous forests. They are most abundant where there are plentiful dead or damaged trees, like in fire-affected areas.

The reproductive methods of Spruce Bugs set them at odds with loggers.

Females use their strong mandibles to chew holes in the bark of dead or dying trees to deposit their eggs. When the eggs hatch, the larvae excavate tunnels in the wood while feeding on the inner bark, cambium, and outer sapwood.

Loggers find that these tunnels damage the wood and allow in wood-destroying fungi. However, these bugs are part of natural forest succession. They have been negatively impacted by certain logging practices like clear-cutting, which disrupts natural patterns.

#17. European Mantis

Mantis religiosa

Adults typically measure 1.7 to 3.5 inches (4.2 to 8.8 cm) long.
Adults may be shades of green, yellow, brown, or occasionally black.
They have triangular heads and distinct “bull’s eye” marks on their forearms.

These funny-looking insects are native to Europe but have established themselves in Colorado. They’re the classic “praying mantis” you are probably familiar with.

European Mantises rely on this excellent camouflage as part of their ambush hunting strategy. Their specially adapted, spiked forearms help them snatch any prey that happens by including other mantises.

Female mantises have earned a nasty reputation for eating their mates. Thankfully, for the males, this only happens about 30% of the time.

Males must try to approach females without being spotted. They use a “stop and go” tactic, as mantises are good at spotting movement but not stationary objects.

If a female spots an approaching male, she’ll eat him, starting with his head. Oddly, males can sometimes still mate headless. 🙂

#18. Pallid-winged Grasshopper

Trimerotropis pallidipennis

Adults may grow to 1.5 inches (3.8 cm) long.
Adults are variable in color but are primarily gray or gray-brown with dark bands on their forewings and yellowish hind tibiae.
Their hind wings are long, narrow, and pale yellow with greenish or bluish at the base and a narrow dark band.

These drably colored grasshoppers typically live in deserts or dry areas with sparse vegetation and bare ground like roadsides, vacant lots, and fields. Their coloration helps them blend in with the ground.

Some of the Pallid-winged Grasshopper’s behavior in Colorado is dependent on temperature.

They tend to spend time foraging when temperatures are 75–90 °F (24–32 °C) and breed when they are 86–104 °F (30–40 °C).

Occasionally, Pallid-winged Grasshoppers will have localized population booms that can cause severe damage to vegetation and crops. These outbreaks may last a year or two.

Rainfall is a major factor in the survival of Pallid-winged Grasshopper eggs. The large outbreaks of these grasshoppers are associated with above-average rainfall levels in the previous fall, winter, and early spring.

Learn more about the bugs that live in Colorado:

Check out these ID guides that focus specifically on different insect families in Colorado.

Do you need additional help identifying insects in Colorado?

If so, check out this excellent ID guide!

National Audubon Society Field Guide to Insects of North America