''Micrathena gracilis'' is a spider in the family

Araneidae Orb-weaver spiders are members of the spider family Araneidae. They are the most common group of builders of spiral wheel-shaped webs often found in gardens, fields, and forests. The English word "orb" can mean "circular", hence the English name ...

(orb-weavers), commonly known as the spined micrathena or castleback orbweaver. This spider spins a moderately large (can be about 20 cm long in diameter) and very tightly coiled web. The spiders themselves are small and can be found to be anywhere from 4.2 mm to 10.8 mm long. Its venom is harmless to humans. ''M. gracilis'' is unique in appearance due to its large spiky abdomen and black and white bodies. Certain spiders of this species can also display a yellow color on the sides of their bodies. These spiders can be seen most active during the end of the summer and beginning of fall. ''M. gracilis'' is diurnal and are rarely ever seen active at night.

Physical characteristics

Females are 8–10 mm long. They exhibit a bulbous abdomen with spines. Males exhibit a fair amount of

sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...

. They tend to be a fraction of the size of the females. Also, they have fewer spines, a flatter abdomen, and a slightly lighter tone. Although males can produce silk, they mostly use it in the mating ritual. File:Micrathena gracilis web.jpg, The central portion of a web File:Spined micrathena bottom.jpg, View from underneath File:Micrathena gracilis-female lateral.jpg, Female lateral view File:Spined Micrathena - juvenile male anterior (Micrathena gracilis).jpg, alt=Spined Micrathena - juvenile male anterior, Juvenile male anterior

Webs

When constructing webs, the inner orbs of their webs are changed every night; however, they may keep the outer layer of the web the same for multiple days.

Distribution and habitat

''Micrathena gracilis'' is native to North and Central America. These spiders tend to wander and rarely ever remain in the same web site for more than week. On average, they spend about 6–7 days on each web site. They are neotropical forest spiders and can be found more easily in hardwood forests that contain Oak and Hickory trees. They tend to like moisture; they are more easily found in woodland forests that are near a lagoon, pond, or other small bodies of water. One study mentioned that these spiders were found in an area that tends to flood during their mating season. M. gracilis may also coexist within and along the edges of colonies of '' Metepeira incrassata'', also known as the colonial orb-weaving spider. They prey on the skimming bluet and are in turn eaten by white-eyed vireos.

Life cycle

''Micrathena gracilis'' hatches in the spring, the image of an adult. After the summer's growth, the female lays eggs in a sac. These remain relatively dormant through the winter months. The general life span is one year in length.

References

External links

Spined Micrathenas (Fairfax County Public Schools site)Spined Micrathena

Pictures of ''M. gracilis''

{{Taxonbar, from=Q2380631 Araneidae Spiders of North America Spiders of Central America