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Insect Identification

Arrow-shaped Micrathena Spider - (Micrathena sagitatta)

Authored By Staff Writer | Last Updated: 2/24/2014

A spider with spines! It's a good thing the Arrow-shaped Micrathena Spider is so tiny.

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The spiny ridges on females are believed to ward off predators, but some sources believe they add to her ability to conceal herself in her web. Males do not have spines and are mostly black with white edges. Females are twice as large as males. Both have ab abdomen that actually gets wide as it nears the end of the body.

Both genders spin orb-shaped spiral webs that lie in a vertical plane (up-and-down). They may only be a few feet off the ground. A short zig-zagged strand of webbing called a stabilimentum may be just above the center of the web. Spiral strands radiating from the center allow the spider to tread easily on its web. Orbweavers are known to rebuild their webs every day.

In autumn, a female will lay eggs on the edge of her web, usually on a leaf right next to it and then die before they hatch. The eggs will overwinter and hatch the next spring. These spiderlings will start out with longer abdomen than adults as well as short, stubby spines.

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Category: Spider
Common name: Arrow-shaped Micrathena Spider
Scientific Name: Micrathena sagitatta
Other Names: Arrow Spider

Taxonomy:
  Kingdom: Animalia
   Phylum: Arthropoda
    Class: Arachnida
     Order: Araneae
      Family: Araneidae
       Genus: Micrathena
        Species: sagitatta

Adult Size (Length): 4mm to 9mm (0.16in to 0.35in) COMPARE

Identifying Colors: red; yellow; black; orange; white

General Description: pointy, holes, thorny, spiny, venomous


North American Reach (Though Not Limited To*): Alabama; Arkansas; Connecticut; Delaware; Florida; Georgia; Illinois; Indiana; Iowa; Kansas; Kentucky; Louisiana; Maine; Maryland; Massachusetts; Michigan; Minnesota; Mississippi; Missouri; Nebraska; New Hampshire; New Jersey; New Mexico; New York; North Carolina; Ohio; Oklahoma; Pennsylvania; Rhode Island; South Carolina; Tennessee; Texas; Vermont; Virginia; West Virginia; Wisconsin; Mexico


* Keep in mind that insect reach is not governed by lines on a map and therefore may appear in areas/regions/states beyond those listed above.


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