Caterpillars make home security systems out of silk
15 Oct 2008, 1554 Hrs

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Washington, October 15 A study has revealed that metalmark moth caterpillars make home security systems out of silk.

The new finding attains significance because, thus far, spiders were considered to be the only animals to detect tremors in their webs caused by foreign objects.

Researchers behind this discovery have revealed that some caterpillars in the genus Brenthia have the capability to sense disturbances, and that they use threads in their silk shelters like tripwires.

"I noticed that the caterpillars kept a couple of really long hairs in contact with the silk shelter, and was curious whether they were using the silk lines of the shelter as a predator detecting system," National Geographic quoted lead study author Jadranka Rota, a biologist at the Smithsonian Institution in Washington, D.C., as saying.

The researcher further said that this findings might be helpful in understanding the evolution of animals that use silk to detect intruders.

"The metalmark [moth] is probably not alone," said Lee Dyer, an ecologist at the University of Nevada in Reno who was not involved in the study.

"There are a lot of silk-weaving caterpillars. I think we are going to find this behavior in a number of other species," Dyer added.

Metalmark moth caterpillars are known to build protective shelters out of silk on the leaves where they dwell. The larvae chew small holes beneath the shelters to use as escape hatches when danger nears.

Rota joined forces with David Wagner of the University of Connecticut in Storrs, and set up a filmed experiment to study the caterpillars' behavior when they were disturbed in different ways.

Eighteen Brenthia monolychna caterpillars were brought into the lab, and allowed to spin their shelters on leaves. Half of the shelters were subsequently taken away.

The researchers used pencils to gently tap either the silk strands of the remaining shelters or the regions on the leaves where the removed shelters had been connected.

They also tapped the edge of the leaves and the caterpillars themselves to see if the animals' responses differed.

The team observed that when either the caterpillars or the silk strands were touched, the caterpillars bolted through their escape hatches and onto the other side of the leaves.

The fastest of them did so in just a hundred thousandth of a second.

The caterpillars, however, did not respond when the scientists tapped the edges of the leaves, or the regions where shelters had been removed.

"This tells us that caterpillars and spiders have separately evolved the ability to use their silk threads in very similar ways," Rota said.

An article on the research has been published in the journal Animal Behaviour. (ANI)