Spined Micrathena

Micrathena gracilis

Copyright, Charles S. Lewallen

The Spined Micrathena is one of our most common spiders. If you've ever walked through a spider web in the woods, it was very likely a micrathena's web.

Usually, it is only the female spider that is seen. She is about 1/2 inch long, with a chunky abdomen that has ten spines on it. The abdomen varies in color; usually it is whitish, yellow, or brownish-black. The cephalothorax (front section) is much smaller than the abdomen, and it is amber-colored. This spider's legs are glossy black.

Copyright, Richard Bradley, Spiders In Ohio

Copyright, Jeffrey K. Barnes

The male Spined Micrathena is about half the size of the female. It has only a couple of spines and a much flatter abdomen. Only females build webs.

To trap prey, the Spined Micrathena builds her web between shrubs or small trees, three to seven feet off the ground. Insects that try to fly in between the trees don't see the web and get stuck. First, the micrathena weaves three main lines of web; then she builds her orb (circular part of the web). The orb is six to eight inches across. As soon as the sun goes down, she eats her web. When the sun comes up, she builds it again. The silk for the web comes from the tip of her abdomen. She weaves the silk with her hind legs.

Most of the prey that get caught in the web are small flies, such as mosquitoes and gnats. Small wasps, flying ants, and beetles also get caught. The micrathena hangs out in the center of her web, with her head pointing down. As soon as she feels the vibrations of prey trapped in her web, she runs to bite it. These spiders are slow and clumsy. Many insects escape before she can catch them. When she catches one, she bites it first, then wraps it in silk.

Male micrathenas do not build webs, but they do weave a "mating thread." The male finds a female's web, and weaves his mating thread onto her web. When he's ready, he quickly runs out and mates with her. Males often do not survive the encounter.

The female makes a tan sphere with silk and lay her eggs inside it. She lays the sphere on plants near her web. Eggs are laid in September.

Spined Micrathenas have only one generation each year. Eggs overwinter in their sac and hatch the next year. Young spiders become fully grown by July and are ready to mate.

Copyright, Tam Stuart

Mark Moran

Mark Moran

Predators of micrathenas include the usual spider-eaters, such as birds, toads, frogs, and lizards. Female micrathenas build an "escape line" into their web. They also make a low-pitched buzzing sound when they are disturbed. You can hear it if you're very close to the web.

Copyright, Cirrus Digital Imaging

Relationships in Nature:

PREY
PREDATORS
SHELTER
OTHER

Asian Tiger Mosquito

Five-lined Skink

Flowering Dogwood

Bald-faced Hornet SP

Fungus Gnat

Red-backed Salamander

Green Hawthorn

Fragile Forktail FP

Crane Fly

Carolina Chickadee

Smooth Sumac

Blue Bottle Fly

Tufted Titmouse

Highbush Blueberry

Northern Caddis Fly

Downy Woodpecker

Red Maple

Virginia Pine Sawfly

American Robin

Witch Hazel

Giant Willow Aphid

American Toad

Greenbrier

Green Lacewing

Eastern Bluebird

Poison Ivy

Dogwood Borer

Eastern Mole

Sassafras

Bald-faced Hornet

Least Shrew

American Hornbeam

Buffalo Treehopper

Wild Turkey

American Beech

Organ-pipe Mud Dauber

Wood Frog

Virginia Pine

Fragile Forktail

Spotted Salamander

Black Cherry

Northern Ringneck Snake

Spicebush

Northern Bobwhite

Wild Grape

Brown-headed Cowbird

Virginia Creeper

Six-spotted Tiger Beetle

Climbing Bittersweet

Organ-pipe Mud Dauber

Relationship to Humans:

Spined Micrathenas can be a nuisance to people when someone walks through their web. It is usually this spider's web you end up pulling out of your hair when you walk through the woods. Really, though, these spiders are a big help to people. They trap lots of small pesky insects, such as mosquitoes and gnats.

SCIENTIFIC CLASSIFICATION

KINGDOM
Animal
PHYLUM
Arthropod
CLASS
Arachnid
ORDER
Araneae
FAMILY
Araneidae
GENUS
Micrathena
SPECIES
Micrathena gracilis

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