Micrathena gracilis female
Micrathena gracilis is commonly encountered in wooded locations, including landscaped residential and suburban locales. This spider is frequently overlooked because of its small size. But hikers would recall the strong silk dragline that it stretches across trails at about the eye level. It is found in most states east of the Rocky Mountains.
The spined micrathena is a somewhat bizarre orbweaver. The females are typically black with white markings and have five pairs of black cones/spines/ conical tubercles encircling the lateral margins of the abdomen. The underside of the abdomen is cone shaped. There is great variability among these spiders. Many are mostly white and may have orange or brown spots. The more typical pattern and coloration found in Pennsylvania are represented in the photo. Males look quite different from females. They have elongated and more flattened abdomens that are blunted at the posterior. Females are 7.5 to 10 millimeters in length, while males are 4.5 to 5 millimeters long.
This species overwinters in the egg stage. Males and females mature in early summer, and females can be found until October. Webs are built along flyways and trails that have bushes and vegetation spanning about 6 feet apart.
This spider is not known to bite people and is probably not medically important.
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Authored by: Steve Jacobs, Sr. Extension Associate