Longterm Welfare for the Insect Kingdom and for Our Forest Floor


An amazing amount of nutrition remains locked in a newly fallen limb until it is released through decomposition. In a paper, Invertebrates of the H.J. Andrews Experimental Forest, Gary L. Parsons and others decribe over a hundred and fifty species of arthropods on a dying Douglas Fir limb. Wood feeders, predators and parasitoids form a not always so congenial community but work towards a common end, survival. Bark beetles are some of the first insects to invade the fallen limb, feeding on the cambium layer.

Joining them in the rampage are Ambrosia Beetles, Trypodendron lineatum, burrowing into the sapwood. Innoculating their first tunnels with an array of bacteria, fungi, nematodes, phoretic mites, and protozoans, the Ambrosia Beetles amass a great army. When the bark beetles' larvae emerge from chambers beneath the cambium, the Dolichopodid fly's larvae are waiting to devour them. The abandoned beetle larvae chambers become host to yeasts, bacteria and the fruiting bodies of fungi. "Fungi mobilize nutrients out of the wood and translocate them to the fruiting structures in the gallery, providing a basis for a complex ecosystem."

Hyphae and spores, which have developed in the gnawed cambium, serve as food for microarthropods (springtails, oribatid and prostigmatid mites) now thriving in the abandoned chambers. Joining in the feast are the larvae of sciarid flies and mycetophagid beetles feeding on the growing beds of fungi.

Self-serving by nature, the larvae of another fly, Drosophila montana, chew on the fungi to encourage yeast growth, which they then happily consume. After a year, nematophagous mites feed upon an endless supply of nematode worms that live in the galleries, feeding on the remaining cambium. Taking several years to mature, additional wood-boring beetle larvae emerge and began munching their way deeper into the decomposing limb, thus opening the way for additional arthropods and microrganisms.

Many of these feeders, embracing a diet of heartwood and sapwood, have developed incredibly "intricate symbiotic relationships with gut-inhabiting microbes," all so our forest floors can promote continued growth. Why not leave that downed limb on the ground for our arthropod friends?


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