Webs React to Electrically Charged Insects

Biological Strategy

Garden cross spider

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Manage Impact

An impact is a high force or mechanical shock that happens over a short period of time, such as a hammer hitting a nail rather than a hand pushing slowly against a wall. Because of their speed and force, impacts don’t allow materials to slowly adjust to the force, which can lead to cracks, ruptures, and complete breakage. Therefore, living systems have strategies that can absorb, dissipate, or otherwise survive that force without the need to add large amounts of material. For example, the Toco toucan’s large beak is very lightweight, yet can withstand impacts because it’s made of a composite material with rigid foam inside and layers of a hard, fibrous material outside.

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Capture, Absorb, or Filter Liquids

The most common liquid used by living systems is water, which they require to survive. But there are many other liquids that provide nourishment, play a role in defense mechanisms, or serve other purposes. Water varies in its availability; it is sometimes plentiful and sometimes very scarce or only available as fog or mist. To minimize the energy required to capture, absorb, or filter liquids, living systems have strategies that take advantage of the unique properties of the given liquid. For example, water moves from a gaseous to liquid state when it encounters a surface colder than the air. Plants in forests that experience fog and clouds more than rain have strategies that condense liquid water from moist air.

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Capture, Absorb, or Filter Organisms

Many living systems must secure organisms for food. But just as one living system must capture its prey to survive, its prey must escape to survive. This results in capture and avoidance strategies that include trickery, speed, poisons, constructed traps, and more. For example, a carnivorous plant called the pitcher plant has leaves formed into a tube that collect water. Long, slippery hairs within the tube face downward. When insects enter the tube seeking nectar, they lose their footing and slide inside, unable to climb out and escape being eaten and digested by the plant.

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Arachnids

Class Arachnida (“spider”): Spiders, mites, ticks, scorpions

Arachnids get a bad reputation, but they play an important role in the ecosystem by controlling insect populations. Almost half of the species in the class are spiders, and most live in terrestrial environments. Unlike insects, most arachnids have two body sections: the cephalothorax, which is the head and thorax fused together, and the abdomen. Mites and ticks, on the other hand, have only one body section that is relatively flat. This body shape comes in handy for the species that are parasitic, because it makes it harder for their hosts to bite or scratch them off.

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Threads that make up the orb-web of the cross spider experience deformation when a positively charged insect enters the neutral or negative field through electrostatic attraction.

Cross spiders, also known as European garden spiders, belong to a group of spiders that are known for constructing orb-webs. An orb-web experiences crossing in the center; please see the gallery for an example of an orb-web. It is believed that the silk threads of orb-webs remain at a neutral or slightly negative charge. Insects, such as honeybees, can collect positive charges when flying through the air or interacting with areas of high positive-ion concentration. If an insect develops a positive charge and flies or walks past an orb-web, the opposite charges interact electrostatically causing an immediate attraction. Threads on orb-webs of the cross spider have been observed to deform from their regular shape as a positively charged insect passes by. This may provide insight in a more sustainable way to capture pests in our gardens and maybe someday even our farm fields (without the use of harmful pesticides).To see for yourself, please view the research video