Bark Beetle

Not all bark beetles feed on tree bark. Some species feed on fruits, seeds, and other parts of the plant 

Summary

The name bark beetle refers to any of the over 2000 species of beetles of the subfamily Scolytinae. They’re called bark beetles mainly because of their tendency to bore into and feed on the inner bark of trees. However, not all bark beetles feed on tree bark. Some species of bark beetles, such as the Southern pine beetle (Dendroctonus frontalis), are considered major pests that destroy conifer forests across North America, while the Coffee berry borer (Hypothenemus hampei) is a major pest of coffee plants all over the world.

Bark Beetles Species, Types, and Scientific Name

Bark beetles are insects in the subfamily Scolytinae. The group also includes some members of the subfamily Platypodinae. This clade of beetles, which provides for more than 2000 species of insects, was previously a separate family but is now considered a specialized group in the true weevil family Curculionidae. 

The true weevil family where this beetle belongs is considered one of the largest animal families with more than 6800 genera and over 83,000 species of beetles. Bark beetles look remarkably different from other members of the true weevil family because they possess modified mouthparts for boring into wood. 

The name bark beetle is a reference to the fact that many species in this group bore into the bark (the phloem layer) of woody plants. However, not all species bore into tree bark. Some feed on fruits and seeds or even tunnel deep into herbaceous plants. 

Some of the most notable members of this group include the European elm bark beetle (Scolytus multistriatus), the large elm bark beetle (Scolytus scolytus), and the American elm bark beetle (Hylurgopinus rufipes). Others include the coffee berry borer (Hypothenemus hampei), which is a pest of coffee plants in Europe, and the Southern pine beetle (Dendroctonus frontalis), which attacks conifer forests in North America. 

Appearance: How to Identify Bark Beetles 

Bark beetles are small bugs with cylindrical bodies. Individuals are hardly larger than a grain of rice. Most species are less than 6 mm (0.25 inches) in length. They’re difficult to see, and their activities often go unnoticed because they’re often scattered. They can be brown or black, depending on the species. Their morphology is slightly different from other beetles in the Curculionidae. 

Bark beetles are characterized by small appendages and antennae which they can easily retract or fold into their body. They typically make tunnels in trees and use their large mandibles to excavate woody tissue as they bore. Bark beetles typically have flattened eyes. Scientists have theorized that their eyes are adapted to seeing in low-light conditions. 

Habitat: Where to Find Bark Beetles

Different species are found across various locations all over the world. They’re mostly tree-boring insects. However, different species of bark beetles target specific types of trees. 

For instance, the elm bark beetles are mostly found on elm trees. They form intricate galleries on the tree surface right under the bark. Similarly, most species of Ips and Dendroctonus beetles attack pine trees. The clover root borer is also a type of bark beetle, and it is found on clover trees. 

While the different species of ambrosia beetles are notable for their impact on timber trees, most species of bark beetles restrict their activity to only one part of the tree, such as the stem, branch, root collar, or twig. Some species only target one type of tree, while others can be found on different species of trees.  

Diet: What Do Bark Beetles Eat?

Bark beetles feed on the wood tissues of various tree species. Most species feed on weak and dying trees. They commonly target spruce, hemlock, and fir trees. In forests, these beetles serve a very important purpose of aiding the decomposition of dead or dying wood. This helps in the renewal of forest trees. However, a few species like the mountain pine beetle attack healthy pine trees. Ambrosia beetles also target timber trees. These beetles are prolific pests that cause serious problems for the timber industry. 

What Eats Bark Beetles?

Adult three-toed woodpeckers prey on both the adult and larvae of bark beetles. They can use their beaks to strip the bark of infested trees in order to reach the insects underneath. This foraging habit indirectly kills beetle broods that they’re unable to reach since it exposes them. Some other birds may also pick these beetles and feed on them. 

A few predaceous beetle species attack bark beetles. Examples of these include the black-bellied clerid and trogositid beetle. Some parasitic wasps are natural enemies of these beetles. However, these insects cannot control bark beetle populations effectively.

Prevention: How to Get Rid of Bark Beetles

Not all species of bark beetles are problematic. In fact, some species are considered beneficial because they aid the decomposition of dead trees. However, some species are known to attack healthy trees and can cause significant commercial damage. 

Once bark beetles infest a tree, there’s practically nothing you can do to save the tree. Currently, no approved chemical insecticides can kill the beetles under the bark. A few trees are able to fend off an attack on their own by producing chemicals that limit the insect’s ability to process woody materials or even immobilize and kill the attacking insect. 

Once an infested tree has been identified, cutting it down promptly or isolating it from other trees will help prevent the spread of the insect. Preventive treatment of your trees, especially during periods when they’re likely to be stressed (such as during drought season), is recommended to help them fight off invading insects. Certain insecticides may be effective in preventing attacks from taking hold. Treatment is best carried out by professionals. Usually, this only applies to high-value tree species that are susceptible to bark beetles. 

Related Animals

• Japanese Beetle
• Ambrosia Beetle
• Dung Beetle