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ZOO-ology column: Diving bell spiders and honeypot ants

Sept. 11, 2011 at 4:11 a.m.

Diving bell spider, Argyroneta aquatica.

By Judie Farnsworth

It lives in an underwater bubble, swims and breathes air - it's the incredible diving bell spider (Argyroneta aquatica).

The name Argyroneta in Latin means silvery net. This spider is found in parts of Europe as well as areas of northern Asia. Its phenomenal adaptation for underwater life is a kind of silky aqua lung called a diving bell (after antique submarines).

The spider spins a submerged, open-bottomed, dome-shaped silk cocoon between pond plants. Its anchor threads serve double duty; alerting the spider to a possible dinner if touched.

The bell is superior to a real aqua lung that needs frequent refilling with compressed air. With gill-like properties, the bell allows gas exchange with the surrounding water. Oxygen is diffused in from the water and carbon dioxide diffuses out. The spider may not need another air bubble for more than a day. The bell will shrink over time, with loss of nitrogen (like helium loss from a balloon) and high levels of activity may require a more frequent "recharge."

When the diving bell is finished, it's off to the surface to collect air bubbles. Tiny water-repelling hairs cover the spider. Some of the hairs trap a thin layer of air that acts like a scuba skin letting the spider breathe while swimming. They help hold a bubble of air between the spinnerets and rear legs. It's released under the bell so it won't rise to the surface.

The process is repeated until the bell is big enough for the spider to enter. The size of the bell varies. A female tends to make a larger diving bell that can be expanded for eggs, spiderlings, food and herself. The males have a sparse bachelor pad.

Diving bell - done. Anchor threads - working. Oops what's going on? A male is building his diving bell right next to the female. He spins a tunnel between them then breaks through her wall - a rather unceremonious courtship. The female makes a chamber for her eggs.

After hatching, the young spiders don't immediately make their own bells. They'll fill empty snail shells with air and use them as shelter for a time. Recycling even short term is a good thing.

Now, off to the arid western U.S.A. where some camels of the insect world live. They're a species of honeypot ants - pantries with feet.

One caste of worker-ants collect nectars and feed larva and sister ants. Another caste of workers is living storage pots called repletes. They gorge themselves on food and liquid brought to them by the other worker caste. Food is stored undigested in a part of their abdomen called the gastor.

They eat so much that their abdomens swell enormously. Repletes are usually found hanging from the ceiling deep in the underground nest. They are quite literally trapped there by their huge abdomens that may be the size of a grape and sometimes transparent.

During droughts or times of need, they will regurgitate and share their stored food with the others in the nest.

They are so valuable that they are sometimes kidnapped by other ants.

In some parts of the world, honeypot ants are a delicacy and eaten by people as sweets. They're the cherry on top of desserts, I suppose.

Judie Farnsworth is a longtime volunteer at the Texas Zoo specializing in educational programs.

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