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In our world bark beetles can bring serious damages to forests which they infest, by killing the tree which they attack when they feed and breed between the bark and the wood of their host.

I am trying to design an alternative bark beetle which, instead of damaging the tree, actually brings benefits to it, so that attacked trees get an advantage from this with respect to a non attacked tree.

Which mechanism could explain such advantage?

  • this beetle still feeds and breeds between the bark and the wood of the host
  • the host is a tree, similar to those we have on Earth. I have not yet decided on a specific biome for the tree to be in.
  • the effect has to be proportional to the rate of infection: the higher the number of beetles in a tree, the higher the advantage it gains
L.Dutch
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3 Answers3

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Trees need to "shed" bark. Beetles help with that

I am going to quickly design a new type of tree. This does not need to be the trees you have but can serve as an inspiration of how to design other ones:

The tree has an outer harder bark during the drier seasons. It helps protect it from the elements. However, during the more peaceful seasons it will attempt to collect water (or sap, if you wish). The inner part of the bark and the outer trunk is more malleable and can "bulge out" with the stored resources.

Which is where the old bark is a problem - it is hard and inflexible like armour. Left in place, it means the tree has a harder time storing more supplies for later.

With this setup, bark beetles can eat the outer bark. This helps the tree to loose the outer bark sooner and sooner start collecting supplies. Which in turn helps the tree grow and develop further.

This does not need to be the setup in your world but there can be any number of reasons trees would not need the outer part of the bark and thus beetles eating it would help out. It could be that other insects nest in the outer layer of the trunk and bark beetles keep them at bay from borrowing further.

At any rate, the premise is some variation of:

  • Tree provides beetle with food
  • Beetle gets rid of bark for the tree

Where the reason the bark might not be needed can vary, depending on what the story or the world needs.

VLAZ
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  • This answer is very plausible because several real trees, e.g. sycamore, naturally shed bark. As a child I saw inner-city trees with irregular patches of exposed new bark, and was told the species was a popular choice for polluted areas because its tendency to shed bark stopped soot building up too much on the tree. – Pastychomper thanks Monica Feb 04 '22 at 10:58
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You could make the beetles do normal symbiotic things with plants like ants do. Seed dispersal, protection from parasitic insects, and fertilization.

They could also be pollinators like moths and bees, or like fig wasps. Fig wasps only lay eggs inside figs and die inside the fruit. Their entire life cycle revolves around the fig. Your beetles could pollinate certain pods that grow on the bark or branches of your tree if the tree is able to self-pollinate. If self-pollination is not available, there could be a mating season in which all the bark-beetles leave the trees and meet up in swarms that would exchange pollen between beetle colonies and thus plants.

frogs2345
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Your beetles eat fungus.

Chestnut blight wiped out the American chestnut forests in the early 20th century.

https://en.wikipedia.org/wiki/Chestnut_blight

The fungus enters through wounds on susceptible trees and grows in and beneath the bark, eventually killing the cambium all the way round the twig, branch or trunk.[30] The first symptom of C. parasitica infection is a small orange-brown area on the tree bark. A sunken canker then forms as the mycelial fan spreads under the bark. As the hyphae spread, they produce several toxic compounds, the most notable of which is oxalic acid.

Your beetles eat the fungus. The more beetles, the more protection the tree has. Usually there will be an equilibrium with a certain amount of fungus and a certain amount of beetles per tree.

Willk
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