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Beetle Senses Forest Fires, Dads versus Cads

by K. M. REESE
August 23, 2004 | A version of this story appeared in Volume 82, Issue 34


Beetle senses forest fires

Zoologist Helmut Schmitz at the University of Bonn, in Germany, figured out in 1999 how the jewel beetle exploits the 3-µm radiation produced by forest fires. Schmitz has since converted the beetle's skill into a sensor that might be used at relatively low cost to warn of such fires. Celeste Biever tells the story in the Aug. 7 New Scientist.

The jewel beetle (Melanophila acuminata), Biever writes, "is legendary among entomologists because it heads straight for [forest] fires rather than trying to escape." The beetle likes forest fires because burnt trees are its preferred home. Fire deactivates resins and others of the trees' defenses that the beetles don't like. A key question was how the beetle could home in on fires from as far as 80 km away.

Schmitz figured out that 3-µm infrared radiation was the clue. The radiation is produced in large amounts from forest fires, escapes most natural atmospheric absorption processes, and can travel long distances. The jewel beetle, Schmitz found, contains clusters of deformable spheres between the thorax and second pair of legs. These spheres contain internal bonds that vibrate only when excited by IR radiation at 3 µm. The vibration triggers associated nerves.

Schmitz has devised a sensor that mimics the beetle's behavior. The sensor is made of polyethylene whose bonds also react to 3-µm IR radiation. The polyethylene expands and presses against a piezoelectric crystal, inducing a current in wires attached to the crystal.

Schmitz's sensor has a sensing range of only 2 meters, but Schmitz thinks he can jack it up to detect fires as far as 10 km away. "In principle," he says, "we can expect the same kind of sensitivity as the beetle from this device."

Staff Chief Daniel J. Lang of the California Department of Forestry & Fire Protection finds Schmitz's idea interesting but wants to evaluate a working prototype of the sensor system before passing judgment on its cost-effectiveness.


Dads versus cads

The University of Michigan's Michigan Today carries in its summer issue a report titled "Dads vs. Cads: A study of female preferences for partners." Topics like this are often said to involve chemistry, so here goes.

The report opens with "Love and Friendship," a poem of 1846 by Emily Brontë:

Love is like the wildrose-briar;<br > Friendship like the holly-tree.<br > The holly is dark when the rose-briar blooms,

But which will bloom most constantly?

That, apparently, is the big question. For long-term relationships, women seem to prefer dads, "men who are kind, compassionate, and monogamous," according to Daniel J. Kruger, a social psychologist at the University of Michigan's Institute for Social Research, and his coauthors Maryanne Fisher and Ian Jobling. But for short-term relationships, the three found, women choose cads, defined by Webster's as men "without gentlemanly instincts" and defined in the Michigan Today report as "the classic romantic dark heroes who are socially dominant, promiscuous, and daring."

The researchers tested evolutionary mating theories "by having the study's subjects, an ethnically diverse group of 257 female undergraduates at a large Middle Western university, read hypothetical scenarios involving classic cad-and-dad character types from 18th- and 19th-century British literature." The results appeared last year in the journal Human Nature [14, 305 (2003)].

About 80% of the participants said they preferred dads over cads for marriage, and 60% preferred cads when considering a brief affair. Kruger and his colleagues say their findings "imply that the dad-versus-cad distinction is intuitive to women and remains a key element of contemporary mating strategies." The idea is that "even if cads aren't good bets to stick around and help raise children, the genes that make men successful cads will be passed along to their sons, who will increase their mothers' eventual reproductive success by providing numerous grandchildren."

However, the participants showed a strong preference for dads as potential sons-in-law. According to Kruger: "A cad would be less likely to provide paternal support for offspring, which means that a daughter might turn to the maternal family for help. That could adversely impact the grandmother's overall reproductive success."


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