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Sicarius

Six-eyed sand spiders

Greta Binford
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taxon links [up-->]African Sicarius [up-->]Central and South American Sicarius [down<--]Sicariidae Interpreting the tree
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Tree from Binford et al. (2008).
Containing group: Sicariidae

Natural History

Sicarius are ground-dwelling species and occur in dry forests and deserts throughout Southern Africa, South America and Central America.  They do not spin webs as retreats or for prey capture.  Instead, they bury themselves in a layer of soil where they live and wait to ambush prey.  During self-burial, soil particles adhere to the thousands of tiny, specialized setae (hairs) covering their bodies and cover the spider, transforming it's natural coloration to the color of the environment.  Sand-covering is thought to be a form of camouflage for these spiders.

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Left: A Sicarius in the field in Argentina, covered in sand. © 2004 Greta Binford. Right: Thousands of microscopic setae, or hairs, cover Sicarius. © 2005 Greta Binford.

The setae covering Sicarius possess long, nanometers thin "hairlettes" protruding from them that have been observed to adhere directly to particles under a scanning electron microscope.  Mathematical models suggest that particles of the size range that stick to Sicarius are able to adhere to hairlettes via weak molecular forces, such as van Der Waals.  Hairlettes are thought to be an adaptation conferring sand adhesion in Sicarius since an identical setal morphology has evolved independently in the Entelegyne spider genus Homalonychus, which also cover their bodies in dry soil particles, and particles fail to adhere as densely to the bodies of related genera that lack hairlettes.

Click on an image to view larger version & data in a new window
Click on an image to view larger version & data in a new window

Left: Particles adhere to the setae covering the exoskeleton of Sicarius.  Right: Sicarius setae have long, thin hairlettes protruding from them that adhere directly to particles, perhaps by intermolecular forces. © 2005 Greta Binford.

Other Names for Sicarius

References

Binford, G.J., Callahan, M.S., Bodner, M.R., Rynerson, M.R., Berea Nez, P., Ellison, C.E., Duncan, R.P. 2008. Phylogenetic relationships of Loxosceles and Sicarius spiders are consistent with Western Gondwanan vicariance. Molecular Phylogenetics and Evolution 49:538-553.

Duncan, R.P., Autumn, K., Binford, G.J., 2007. Convergent setal morphology in sandcovering spiders suggests a design principle for particle capture. Proceedings of the Royal Society B: Biological Sciences 274 (1629), 30493056.

Information on the Internet

Title Illustrations
Click on an image to view larger version & data in a new window
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Scientific Name Sicarius terrosus
Location Parque Sierra de las Quijadas, Argentina
Creator Dr. Kenneth Cramer
Specimen Condition Live Specimen
Image Use creative commons This media file is licensed under the Creative Commons Attribution-NonCommercial License - Version 3.0.
Copyright © 2005 Dr. Ken Cramer
Scientific Name Sicarius albospinosus
Creator Dr. Kenneth Cramer
Specimen Condition Live Specimen
Image Use creative commons This media file is licensed under the Creative Commons Attribution-NonCommercial License - Version 3.0.
Copyright © 2005 Dr. Ken Cramer
About This Page

Greta Binford
Lewis & Clark College, Portland, Oregon, USA

Correspondence regarding this page should be directed to Greta Binford at

All Rights Reserved.

Citing this page:

Binford, Greta. 2009. Sicarius. Six-eyed sand spiders. Version 24 February 2009 (under construction). http://tolweb.org/Sicarius/129538/2009.02.24 in The Tree of Life Web Project, http://tolweb.org/

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For a more detailed explanation of the different ToL page types, have a look at the Structure of the Tree of Life page.

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