Renewable Revolution

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Life (Re)Cycle

God's Inordinate Fondness for Beetles 

Death breeds life in the world’s most diverse and abundant group of animals.

By Bernd Heinrich | August 1, 2012

An inordinate fondness for beetles.” That reportedly was the wry retort of famed British biologist J.B.S. Haldane to a theologian who asked him if anything could be concluded about the Creator’s predilections by studying creation. Haldane was referring to the fact that there are nearly half a million beetle species known on Earth. Having been an avid beetle collector since I was a small boy, I can say I share a certain fondness for the insects.
 
The diversity of beetles on our planet is amazing, and their behaviors and life histories are just as varied. Nowhere is this more evident than in beetles that dine upon carrion. I find carrion beetles not only wonderfully diverse, but also emblematic of natural cycles of birth and death, the focus of my latest book, Life Everlasting.
 
As a scientist, I worked for years on the behavior of ravens, the ultimate carcass-disposal specialists, so I was not particularly mindful of the roles beetles play in the recycling process. While large scavengers, such as ravens, eagles, wolves, and coyotes, quickly dispose of animal carcasses in snowy Northern Hemisphere forests, insects take the recycling lead in summer. One group in particular, the burying beetles, or nicrophorines, bury whole carcasses to create an underground smorgasbord for their larvae.

Burying beetles are conveniently attracted simply by setting out a dead mouse. After one beetle discovers a fresh carcass, it wafts an attracting scent to “call” a mate, who arrives in minutes. The pair transports the carcass to a suitable burial site and inters it there.
 
The fate of large animal carcasses, such as moose or deer, may be similarly quick, and it usually involves large scavengers as well as small. Plant carcasses present a more complicated challenge, however, and the disposal of dying and dead trees may take decades, sometimes even centuries.
 
Because it is a process that proceeds at a glacial pace, the decomposition of a tree is not as flashy as a hyena killing an ailing antelope, or even the burying of a mouse by a pair of Nicrophorus beetles. So the fate of dead trees and the roles that beetles play in it are therefore easily taken for granted, especially since one seldom sees the beetles as adults—they come, lay eggs, and leave, and the larvae then stay hidden inside for months or years. Yet the beetles use the tree as a food source, and thereby help degrade its tissues and recycle its remains into other organisms as surely as burying beetles do those of mice and birds.
 
Peel back the bark of almost any tree that is dying or recently dead, and you find the fantastically patterned feeding galleries of beetle larvae, primarily members of the family Scolytidae.

Each beetle species leaves distinctive tracks, and each specializes in depositing eggs in a narrow range of tree species. Digging deeper inside the dead tree, one encounters long-horned beetles (Cerambycidae)

and emerald beetles (Buprestidae),

their much larger larvae move from gnawing the cambium, part of the plant’s vascular system, to burrowing deep into the xylem at the heart of the tree.

Reminded day and night in the summer when I hear the chewing of sawyer beetle grubs in elderly trees,

I think of the thousands of gorgeous beetle species in woods the world over that make forest life possible. The topic of disposal of the dead is reminiscent of metamorphosis, and is key to the ecology of life everlasting. Beetles occupy a major hub of it. Haldane had more reason to be correct than he may have realized.
 
Bernd Heinrich is an internationally recognized scientist and the author of numerous award-winning books, including the best selling Mind of the Raven, Why We Run, and Winter World. He is a frequent contributor to national publications and professor emeritus of biology at the University of Vermont.

http://the-scientist.com/2012/08/01/life-recycle/