Forest Ecology and Conservation

[gdebusk]

Originally Posted by fangsheath

The insects in the photo appear to be beetle larvae, but what species I couldn't tell you. Many scolytids are about this size. They may well be the cause of the mortality, bark beetles are often far more lethal to trees than larger wood-borers. But beetle larvae are not usually so species-specific, suggesting that something else is stressing the trees and making them vulnerable.

The odd thing is I saw no signs of galleries under the bark, though the bark had slipped on the trees before it was scaled. The larvae also emerged from holes that went into the wood of the tree. Do Scotylids make pupation chambers that go into the wood like that?

[fangsheath]

There are an awful lot of scolytid species and I don't know all the variations in life history. I know that some of them are strictly bark beetles, not burrowing deeply into the tree, while others burrow into the sapwood or even heartwood. Some species make obvious galleries, while others, such as the black turpentine beetle (which attacks pines) do not make galleries as such, but excavate in groups, removing sizable patches of cambium. And of course I don't know for a fact that these are beetle larvae, possibly they could be carpenter worms or something else.

[gdebusk]

I have often wondered if wood boring beetles excavated their exit holes before or after pupation. I found one reference for the Sugar Maple Borer (Glycobius speciosus (Say), a Cerambycid), that says the exit tunnel is made before pupation:

http://www.animalcorner.co.uk/insect...tle_sugar.html

Does anyone know if this is a common trait of Cerambycids?

[fangsheath]

This reference is somewhat vague on the subject. It's not clear to me what they mean by "outside." It could be the outside of the sapwood, not the outside of the bark. My impression is that the cerambycid larvae often excavate out to the outer edge of the sapwood prior to pupation, but do not penetrate the bark. Since the adults generally have strong jaws capable of chewing through the bark, there is no need to proceed further. It would seem maladaptive to do so, since it would be a beacon to predators.