by Trudy Irvine, Education Committee
Did you know dock spiders don’t make classic spider webs? That they can walk on water and scuba dive for prey for up to 30 minutes? That while they eat mostly aquatic insects, they can tackle minnows, tadpoles, and frogs up to 5 times their size?
Like other arachnids, dock spiders (also known as fishing spiders) hunt by detecting vibrations created by their prey. But instead of webs, water is their hunting ground. With their back legs holding onto the shore, they stretch their body and other legs out on the surface of the water. Special organs in those legs and feet help them discern the direction, the distance, and the likely source of disturbances. Their legs and bodies are covered in fine, hydrophobic hairs, which allow them to float and run on the surface tension of the water like water striders. Quick on their feet, some dock spiders use a silk dragline to prevent them from speeding past their prey.
Air trapped in their hairy bodies also allows them to dive beneath the surface and remain submerged, covered in what looks like a fine, silvery envelope.
The breeding behavior of dock spiders is also interesting. After mating, the male remains attached to the female but will die shortly after, without any interference from her. The female then eats the male to ensure nutrition for rearing her young. Her brood consists of up to 1000 baby spiders in an egg sac, which she carries in her fangs like a cotton ball. When they are close to hatching, she will spin a small, dense web under a dock or in grasses to shelter her spiderlings, and she will stay close by as they develop, earning this species another name of “nursery web spider”.
Do not fear the bite of a dock spider – they are not aggressive and will withdraw when they feel threatened. Bites may occur if they are inadvertently stepped on or handled. Make sure you shake out those clothes you left lying on the dock before you put them back on!
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