|Bark beetle galleries|
Bark beetles, members of the subfamily Scolytinae are actually specialized "true weevils." They are small, usually only 1/16 to 1/4 inch. The female lays its eggs just beneath the outer bark in an egg gallery. After hatching, the tiny larvae tunnel out their own galleries, branching out from their former home. As they grow their tunnels increase in diameter. The tunnels end where pupation occurs and then the adults emerge through holes of their own to start the cycle all over.
Like most insects, our opinion of them depends on how they are encountered. If they are attacking your landscape or fruit tree, they are a pest or worse. Some may only cause limb damage while others such as the mountain pine beetle can decimate forests of the west. Thousand cankers is caused by bark beetles and others can carry plant pathogens such as the Dutch elm disease.
A word in the defense of the bark beetle. Unless they are attacking in epidemic proportions, they do serve a useful purpose as food for woodpeckers and other birds and insects. Most live in dead, weakened, or dying hosts and aid in the decomposition of dead wood while renewing the forest by killing older trees. Some "ambrosia beetle" species farm fungi, eating the products of their crop, even carrying the fungus with them and inoculating new host trees.
|Frass filled galleries of bark beetles|
|Bark beetle galleries, some with brown frass left in|
|Bark beetle galleries and white slime mold- click to enlarge|
|Cockroach, possibly of the genus Cryptocercus|
Because of their location, I suspect these roaches were of the genus Cryptocercus which are wood-eaters. Like termites, they don't have the enzymes to digest wood and depend on protozoans and bacteria that they host in their guts to digest the cellulose into sugars that they can then metabolize.
There is a lot of life in a dead tree. If there weren't, we would no longer have forests, just a hundred foot deep pile of dead trees.