Adult female. Upper Newport Bay, Newport Beach, CA. Beginning 5 Nov. 2005
Longitude W 117.8858718081394; Latitude N 33.65373347788835. © Peter J. Bryant.

Bolas spider

Mastophora cornigera

Araneae: Araneidae

During the day, the female Bolas spider is inactive, although she can often be found in fairly exposed places.  The male is much smaller than the female. The females provide a remarkable example of aggressive mimicry when they release chemicals similar to the sex attractants that are produced by female moths to attract males.  They produce three chemicals that are identical to those produced by the moth.  Thus, the main prey for these spiders is male moths. 

Stowe, Mark K., et al; "Chemical Mimicry: Bolas Spiders Emit Components of Moth Prey Species Sex Pheromones," Science, 236:964, 1987.  Bolas spiders were featured on David Attenborough's TV series "Life in the Undergrowth" (2006).

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Shortly after dusk, the spider lowers herself on silk threads, spins a silk line with a sticky blob on the end of it and swings it to catch the moths or other insects that have been attracted by the chemicals.  The spider gets its name from the bolas (ball-on-a-string) weapon used by Eskimos and South American Indians. © Peter J. Bryant
Here she has caught a cranefly. © Peter J. Bryant

Here she is hauling it in. © Peter J. Bryant
Here she is sucking blood from her prey. © Peter J. Bryant

Here she has caught a moth, wrapped it in silk, and is feeding on it. © Peter J. Bryant
The egg cases of this spider are round balls hanging on silk straps. When discovered, in November 2005 on a kiosk at the Peter and Mary Muth Interpretive Center at Upper Newport Bay, Newport Beach, California, this female had already made eight egg cases and hung them on a web. Two weeks later, another egg case had appeared! © Peter J. Bryant

24 May 2006: Adult male just emerged. © Peter J. Bryant

Adult male on web. Spider provided by Lenny Vincent. © Peter J. Bryant

Adult female and four egg cases. Boat Road, Laguna Beach, Orange County, CA. 10-12-08. © Peter J. Bryant
Adult female. Boat Road, Laguna Beach, Orange County, CA. 10-12-08. © Peter J. Bryant

Female and 11 egg cases. Pelican Point, Crystal Cove State Park, Orange County, CA. 12/2/09. © Peter J. Bryant

Female and 7 egg cases. Pelican Point, Crystal Cove State Park, Orange County, CA. 12/2/09. © Peter J. Bryant

Mission Viejo, CA. 11-30-09. © Suzanne Nevius.
Mission Viejo, CA. 12/2/09. © Suzanne Nevius

Mission Viejo, CA. 11-30-09. © Suzanne Nevius.

Adult female and seven egg cases, on Agave. Upper Newport Bay, Newport Beach, Orange County, CA. 11/17/10. © Peter J. Bryant. Geotagged image - copy jpg and view with Geosetter.
Adult female, on Agave. Upper Newport Bay, Newport Beach, Orange County, CA. 11/17/10. © Peter J. Bryant

Laguna Beach, Orange County, CA. 5/10/2015. © Greg O'Loughlin
Laguna Beach, Orange County, CA. 5/10/2015. © Greg O'Loughlin