Discover 9 Invasive Insects Buzzing and Crawling Around California

Written by Lev Baker
Published: March 29, 2023
© Jim Lambert/
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California is home to several invasive species that negatively affect the natural balance of the local ecosystem. Invasive insects are an annoying presence to humans and are harmful to the native plants in the area. Unfortunately, these invasive insects are incredibly tough to eradicate. Even with extensive efforts, they still affect the Californian ecosystem in many ways.

Here are just some of the many invasive insects in California.

1. Africanized Honey Bee (Apis mellifera scutellata)

Known by its more common name, the killer bee, Africanized honey bees are a hybrid bee species resulting from the crossbreeding of African and European honey bees. They were first introduced to Brazil in 1957 and later spread into North America in the early 1990s. Today, they are invasive insects in California.

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Africanized honey bees are similar in appearance to European honey bees, but they are ever-so-slightly smaller. They are around 0.4 to 0.6 inches long, with a wingspan between 1 and 1.2 inches. They also have darker bands on their abdomens compared to their cousins. Despite these differences, it can be very hard to distinguish between these two types of bees without specialized equipment or knowledge.

Their behavior, in particular, is what makes these bees a pest and invasive species. They have a tendency to be excessively defensive of their hives and colonies and often form swarms. This behavior poses a significant threat to the safety of humans. In fact, over 1,000 people have been killed since their introduction. They also pose a threat to European honey bees! They will compete for food and habitats while displacing the native species.

California’s agricultural commissioner established an action plan to help control the population of the Africanized honey bee. This plan includes educating the public on their presence and behavior and removing the swarms or hives that threaten the public’s safety.

Africanized honeybee
Africanized Honey Bee (Apis mellifera scutellata).


2. Oriental Fruit Fly (Bactrocera dorsalis)

This species of fruit fly is native to Southeast Asia. It has become an invasive insect in California and much of the world. The oriental fruit fly is around 0.3 inches in length and has a striped yellow and brown body with clear wings. Their wings have a black band around them. 

The oriental fruit fly is attracted to ripening fruit and vegetables, especially those with high sugar content. The females will lay their eggs in these foods, which will later hatch and feed on them. This fly can attack more than 230 different fruit and vegetable crops, including citrus trees, avocado, mango, and papaya.

The oriental fruit fly poses a threat to California’s agricultural industry. If left uncontrolled, they could cause huge amounts of damage to California’s crops. This would lead to substantial economic losses for farmers and higher prices for consumers.

To prevent the spread of these pests, the California Department of Food and Agriculture has introduced several safety measures, including setting traps, inspecting and treating produce shipped out of infested areas, and releasing sterile male flies to disrupt the breeding cycle of the pest.

Oriental Fruit Fly (Bactrocera dorsalis).


3. Argentine Ant (Linepithema humile) 

The Argentine ant is a small and slender ant species native to Northern Argentina. The Argentine ant is usually between 0.08  and 0.125 inches long with uniform brown coloration, which makes them easily identifiable. 

Argentine ants are very opportunistic when it comes to nesting. Colony nests have been found in cracks in walls, in the ground, in spaces between boards and timbers, and in other annoying places. Although they do not sting or bite humans, these ants are a nuisance pest in homes, invading food storage and spoiling goods.

Argentine ants have a varied diet that consists of nectar, insects, seeds, honeydew, and more. As a result, these ants affect the balance of the ecosystem by facilitating plant-feeding pest insects and disrupting native ants, pollinators, and vertebrates. 

This invasive species has no known specific predators, making the population much harder to control. Attempts to control Argentine ant populations include chemical and cultural means.

Argentine Ant (Linepithema humile).

©Javier Chiavone/

4. American Serpentine Leaf Miner (Liriomyza trifolii)

The American serpentine leaf miner is native to North America and has found its way throughout the country, including California. It is a small fly-like insect that is typically less than 1/8 inch in length and has a distinctive yellow and black striped body.

These leaf miners are named for their tendency to build tunnels in a plant’s leaves while they feed on the plant itself. The tunnels make a cozy nest for the larvae. They will eat the leaves and tunnel through the interior, creating distinctive serpentine patterns.

The serpentine leaf miner feeds on a large variety of plants, including fruits, vegetables, and ornamental plants. As a result, they cause a large amount of damage to crops, reducing crop yields.

The American serpentine leaf miner is considered an invasive species because it is not native to California and has no natural predators to control its population. As such, their numbers have grown rapidly, and they are causing an exponential amount of damage to plants and crops. Unfortunately, the pesticides used to control these flies also cause harm to other species and the environment.

Yellow cherry tomatoes attacked and damaged by the American serpentine leaf miner (Liriomyza trifolii).


5. Red Imported Fire Ant (Solenopsis invicta)

The red imported fire ant is native to South America and found its way into California in 1998. Since then, these ants have been invasive insects in California, infesting several residential and commercial areas in the state. These dark reddish brown ants vary between 0.06 to 0.2 inches in length, the same as the native harvester ant, and similar in size to the also native southern fire ant. The red imported fire ant has a stinger on the end of its abdomen to protect itself and its nest from invaders.

These ants are very aggressive and territorial and will sting humans and animals to protect their nests. Their nests are built in mounds which are large dome-shaped structures reaching 2 feet in diameter and 1 foot tall. Their diet includes plants, animals, seeds, and other organic matter, which they will bring back to their colony and store for later. 

Having no natural predators in California, the population numbers are thriving. This is creating an imbalance compared to the native ant species. Red imported fire ants have also been linked to changes in the soil structure and damage to crops.

Red Imported Fire Ant (Solenopsis invicta).


6. Ash Whitefly (Siphoninus phillyreae)

The ash whitefly is a tiny insect that is about 0.06 to 0.125 inches in length. They have a white or yellowish body and four white wings that are held in a tent-like shape over their bodies. The ash whitefly uses its piercing-sucking mouth to feed on plant sap. This insect was first introduced to California in the late 1980s. It poses a significant threat to local fruit and shade trees.

Ash whiteflies feed on a variety of plants, including ash trees, which is where they get their name. They are known to be especially destructive to avocado trees, which are prominent in California. They feed on the sap from plants, which can cause damage to the leaves and stems and eventually lead to the death of the plant if the damage is substantial enough.

Historically, the flies have made a huge economic impact in California, particularly in the shade and fruit tree nursery industry, costing hundreds of millions of dollars. In 1992, California introduced a control program for these flies by releasing small parasitic wasps that would attack and kill the ash whitefly. Since then, the numbers have dropped significantly. These insects, thankfully, are no longer considered a major threat to the state. They should not be able to cause such large economic damage in the future.

Ash Whitefly (Siphoninus phillyreae).

©Tomasz Klejdysz/

7. German Yellowjacket (Vespula germanica)

The German yellowjacket is a species of wasp native to Europe. It has become an invasive insect in California. They measure around 0.5 to 0.6 inches long and have a very distinctive black and yellow striped body. 

These wasps are social insects and live in colonies that can include several thousand individuals. They are known for their aggressive behavior and can sting multiple times, causing pain, swelling, and in rare cases, allergic reactions that lead to death.

German yellowjackets are omnivorous and feed on things like other insects, fruits, and nectar. They are also attracted to human food and rubbish, making them a nuisance in residential areas.

Several control methods for German yellowjackets are used in California, including a combination of cultural, biological, and chemical control. The most crucial control method is informing the population about the wasp’s habits and nature and teaching them how to properly dispose of food waste and garbage from outdoor areas to discourage the wasps from congregating.

What do yellowjackets eat- yellowjacket on a strawberry
German Yellowjacket (Vespula germanica).

©Henrik Larsson/

8. Elm Leaf Beetle (Xanthogaleruca luteola)

The elm leaf beetle is an invasive insect in California. It is actually one of the most important urban forest pests in California! This beetle was introduced into the United States in the 1830s and was first detected in California in 1924. Elm leaf beetles are olive-green in color with black stripes and are around 0.25 inches in length when fully grown. 

The diet of the elm leaf beetle is elm plants, from which they get their name. They eat elm foliage and damage the plants. This leads to the loss of foliage, which is aesthetically displeasing and removes shade that the plants usually provide. The damage the beetle causes can weaken trees and increase susceptibility to diseases. This insect can be found wherever there are elm plants — a truly invasive species. 

In addition to damaging elm trees, this beetle can be an annoyance to homeowners as they can gather in large numbers on buildings and other structures. These beetles will leave behind yellow stains on the surface from their excrement.

Elm Leaf Beetle (Xanthogaleruca luteola).

©Guillermo Guerao Serra/

9. Vine Mealybug (Planococcus ficus)

These tiny, soft-bodied insects are native to the Mediterranean region and were first detected in California in the early 1990s. They have since become a significant pest of grapevines and other crops within the state. They are around 0.125 to 0.25 inches long and have a pinkish body covered in a white, waxy coating, giving them a fuzzy appearance. The male vine mealybugs are much smaller than their female counterparts, and they have wings, too, unlike the females.

These insects feed by sucking the sap from plants using their long, thin mouths. In California, these bugs are most commonly found on grapevines, but in other parts of the world, they are also known to infest fig, date plum, apple, or avocado trees.

Vine mealybugs live in large groups composed of adults, eggs, and nymphs and can reproduce very quickly. They can easily migrate to new plants, especially when the foliage is overlapping, and can spread viruses from plant to plant. 

Vine mealybugs can cause a lot of disruption to the grape industry, as they leave deposits of honeydew on the plants, which promote the growth of black mold. As well as this, the vine mealybug can be found within grape bunches, making them unfit for consumption. In addition, because of their waxy bodies, these bugs are resistant to insecticides used to treat them, so parasitic control methods have been adopted.

Vine Mealybug (Planococcus ficus).


The Featured Image

What do yellowjackets eat - yellowjackets on apple
Yellowjackets are more noticeably segmented with a very small waist.
© Jim Lambert/

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About the Author

I have been a freelance writer for the past 2 years. My two biggest loves in the world are music and animals. I have even gone on to start my own personal blog called Frontman Philosophy. I have a huge love of animals and I love building my knowledge of animals through research. I love sea creatures in particular, my favorite being the octopus because of their intelligence, and I mean, come on, what's not to love! I have a rescue boxer named Dante who is the friendliest pup a man could ask for.

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