Moth Antennae Rival Modern Inventions

Press, Volume CVIII, Issue 31774, 3 September 1968, Page 9

Moth Antennae Rival Modern Inventions

WALTER SULLIVAN

Moths, through the hit-or-miss process of evolution, have developed electronic detectors that, in their sophistication and efficiency, rival anything that engineers have been able to produce.

That is the theme of a report published in the August issue of Applied Optics by a Department of Agricluture research worker who has been studying what “turns on" and

“turns off” such moths as the giant night-flying Cecropia. ; When exposed to light, thesel insects drop to the ground and seek darkness as a defence against predators. Dr Philip S. Callahan, the research worker of the department’s Entomology Research Division in Tifton, Georgia, has found that this action is caused by detectors similar to those invented by the Germans during World War II to spot Allied I radar emissions.

They are known as dielectric waveguide antennae. They are hollow and are shaped so as to resonate in the presence

of certain radar or radio; waves. To do so they must be the correct thickness and the electrical properties (dielectric constant) of their material must be correct.

All of these strict requirements are met by tiny spikes near the base of the feathery antennae of night-flying moths. However the spikes are so microscopically tiny that they respond to light waves, rather than radio waves. Experiments in which electrodes, set in place under a microscope, were used to mon-! itor moth nerves showed that; i bright light shining on these; i spikes short-circuited input to i ■ the moth brain from the numerous other sensors on its! antennae.

A moth, thus deprived of sensory input, stops whatever he is doing and goes into hiding.

For man to construct such detectors would be difficult. They are only 26 ten-thou-sandths of an inch long and one-tenth as wide. According to a summary of the finding, prepared by the American Institute of Physics, this is the first discovery of such detectors small enough for sensitivity to light waves.

In an interview Dr Callahar said his chief interest was ir | the sensory apparatus of the I corn earworin moth. Thii ' pest gnaws into corn, cottor and tomato crops, causing ‘yearly damage of $57 millior in California alone, he said. When viewed under < • microscope, he said, the an itennae of the corn earworrr 'moth show some remarkable preceptors. Among the 10 dif i ferent types is a stublike one i surrounded by eight or nint I tiny spikes. The stub is linket [to the brain by a nerve, bu J the spikes lack such a connec I tion and apparently serve onlj as reflectors. Search For Signal

! Other detectors look like| miniature models of the horn antennae atop microwave relay towers and buildings operated by telephone companies. These, Dr Callahan said, !“are highly specialised, very sophisticated detectors of some . sort.” Some, he suspects, pick jup mating smells and food smells by resonating to char--1 acteristic wave lengths emitted by substances of interest to the moths. Dr Callahan’s goal is to find a signal to which these—but no other—moths respond. It could then be used, like the music of the Pied Piper, to lure the corn earworm moth to its doom. Through his research on the larger moths, : such as Cecropia, he hopes to learn enough of moth receptors to plan such an attack on ■ the corn earworm.—Copyright, 1968. New York Times News Service.

A.I.D. international aid programme to wipe out smallpox in Africa will pass the halfway mark this week with the vaccination of the 55 millionth person, according to the Agency for International Development. —Washington, September 2.