On Land: Arachnids
Silver garden orbweaver
Argiope argentata
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About
With their long, spindly legs and distinctive silver, yellow, or white abdomens, the silver garden orbweaver is a striking arachnid to behold. They’re found throughout the Caribbean, as well as in parts of North and South America, and their webs are absolute masterpieces.
Concentric circles of silk form a grid-like pattern to the edges of the web, often with thicker zigzag patterns — called the stabilimentum — near the center that add additional stability to the structure. Both the spider’s body and the silk they spin reflect UV light, attracting and ensnaring unsuspecting pollinators in search of flowers.
Much like other orbweaver species, female silver garden orbweavers are much larger than the males; males usually only grow to be about 30% of a female’s size, not counting leg-length. Male silver garden orbweavers have mating organs on appendages near their head called pedipalps, which break off inside female spiders while mating. This prevents other spiders from mating with the same female in the future, but the males themselves don’t live very long. Once reaching maturity, they typically die either during or immediately after their second time mating … if they make it that far. Even before that, there’s a decent chance they’ll be cannibalized by their first mate — a norm for this species.
Once eggs are laid, female silver garden orbweavers protect their young spiderlings until they’re ready to leave and create their own webs in the world. These spiders rarely bite humans or pets; instead, you may spot one patiently poised at the center of its web, waiting for vibrations caused by an insect crash-landing to signal a successful catch.
Header image by @michaelbakkerpaiva (CC-BY).
This species is:
Native
Why that matters:
Native species are those that evolved in the region naturally, without human influence. That means they’re specifically adapted to Saba’s habitat, and play a key role in island biodiversity. When we lose native species, gaps appear in the ecosystem. That leads to cascades of additional extinctions, and to the loss of the ecosystem services (food, clean air and water, flood and coastal protections, and more) that we humans rely on.
Silver garden orbweavers have striking patterns of silver, yellow, and white on their abdomens — easily visible when they’re poised in the center of their spiral webs. Credit: @michaelbakkerpaiva, iNaturalist (CC-BY).
iNaturalist Observations
Where locals, researchers, and visitors have seen this species.
Google / Imagery © 2023 CNES / Airbus, Landsat / Copernicus, Maxar Technologies, U.S. Geological Survey, iNaturalist Map data @2023
This map shows geotagged observations of this species made on iNaturalist, the world’s largest community-science platform.
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Observations of land species in water:
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Ask a Scientist
Question: How do orbweavers actually spin the silk they use? Where do the raw materials come from?
Answer: Silk is produced by glands inside the spider near the end of their body. The silk is made of proteins and is essentially a liquid while still in the spider’s body. This liquid is squeezed out through structures called spinnerets, which convert it into a solid. Different kinds of spiders make very different types of webs. There are multiple glands and spinnerets that, in combination, produce the types of silk a spider uses to construct its web. For spiders that spin an aerial spiral web, like the silver garden orbweaver, their last step is to lay down tiny droplets of glue along the silk to help grab onto prey.
Dr. Lauren Esposito
Curator of Arachnology and Islands 2030 Co-Director, California Academy of Sciences
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