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A photo shot with a Thermovision camera (top right and bottom left) reveals the heat emitted by a conifer cone.

Seed-eating bug uses infrared dinner detectors

October 30, 2008

A recent discovery by researchers led by SFU biologist Stephen Takács could help stop western conifer-seed bugs (Leptoglossus occidentalis) from devouring millions of dollars worth of cones in B.C.’s conifer-seed orchards.

Takács and his colleagues have determined that the voracious seed predators, which dine exclusively on conifer cones, use special infrared receptors to detect heat emitted by the cones. His findings were reported online Oct. 21 in the Proceedings of the Royal Society B.

The behavioral ecologist’s team made the discovery after noticing that the insects seemed to be drawn to people’s houses during cold weather and wondering whether they were attracted to the houses’ heat.

Through scanning-electron microscopy they discovered that the bugs’ abdominal segments have specialized infrared receptors on them similar in location and texture to those found on Australian fire beetles.

And using an infrared-detecting camera they also discovered that conifer cones are as much as 15 degrees Celsius warmer than their immediately surrounding environment, most likely due to radiation and/or the metabolic activity of seed development.

When the team first trained their Thermovision camera on cone-laden conifer trees, "we were just stunned," Takács told Science News magazine. It was as though the trees were festooned with candles, he said, adding, "all we could think of was Christmas."

The researchers’ lab and field experiments confirmed that the bugs prefer stronger infrared radiation.

Takács says he hopes the discovery will help scientists "build the first mouse-trap for this bug. Right now, the only weapons orchardists have against these destructive bugs are environmentally unfriendly pesticides."
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