About 3,800 species of spiders are known to exist in North America. These species fall into 68 different families, but some of the families contain many more species than others. The Sheetweb Weavers (family Linyphiidae – pronounced "lin-uh-FEE-eh-dee") is a very large family of mostly very tiny spiders. In some parts of the country, a quarter of all the spider species may be Sheetweb Weavers. Many of them are only a couple of millimeters long, or less. And a lot of them look alike – particularly the Dwarf Spiders (subfamily Erigoninae). In fact, the female Dwarf Spiders are actually the only spiders in North America with no key to genus, which means they can't be identified using the standard spider identification guide, Spiders of North America.
LinEpig is an online image gallery designed to make it easier to identify Dwarf Spider females. The name (which we pronounce "LIN-eh-pidge") is a combination of Linyphiidae and "epigynum" – the term for a female spider's reproductive organs. In spiders, the reproductive anatomy is very intricate, and scientists use the details to tell related species apart.
Working with specimens that have been identified by experts, we are using a digital microscope to photograph these anatomical structures, and posting the images in an online gallery for easy reference. By making this online reference available, this Field Museum project helps research collections around the country identify the interesting and diverse linyphiid specimens in their collections.
The Dwarf Spider photos above are by Tom Murray and Kevin Lentz.