© Steve Tessler and MapTheSpider.com -- Images are all of Atypus snetsingeri *

Map The Spider is a Citizen Science project that collects sightings of purse-webs in the Philadelphia region of southeastern Pennsylvania.

About Purse-web Spiders

Purse-web spiders (Infraorder Mygalomorphae, Family Atypidae) are secretive and primitive-looking creatures related to trap-door spiders and tarantulas. They are sometimes called 'atypical tarantulas' because of their unique web and method of prey capture. The purse-web is a sock-like silken tube that is constructed in a burrow below ground where the spiders spend most of their time. The web extends above the ground to either lay horizontally near the ground or extend upward to attach to the base of trees and shrubs. When unwitting prey happen to walk upon the web they are stalked invisibly from inside, stabbed with large fangs through the silk, and then dragged inside where they are slowly eaten...

Visit Bugguide.net (North America) or iNaturalist.org (worldwide) to view photos and accompanying descriptive information for different species of purse-web spiders. Most of the photos are of 'wandering males', some of whom are rather striking and conspicuous. Females and immature Atypids rarely leave their webs where they'd be noticed and photographed, and people usually don't recognize purse-webs as 'webs' even when standing next to them.

North American Purse-web Spiders

In North America there are 2 genera and 8 species of purse-web spiders. The genus Sphodros has seven species, a few of which are widespread, that have been reported east of the continental divide from Minnesota south to Texas and eastward to New England and Florida, with species extending into southern Ontario and northern Mexico. North America also has one other species, Atypus snetsingeri*, originally reported from only two sites in southeastern Delaware County near Philadelphia, Pennsylvania, and considered 'enigmatic' because all other Atypus species are found in Europe, Asia and North Africa.

MapTheSpider - Can you find purse-webs in your neighborhood?

The ultimate goal of this project is to make a range map for the spider, Atypus snetsingeri*, which is found near Philadelphia, PA. To make a map we need to know where the spiders live, and luckily for us the distinctive vertical purse-webs can be seen at any time of the year (the spider is hidden in a burrow). Because the web alone is not diagnostic for a species, the second phase of the project will visit some of the reported sites to examine the spiders and make a species determination. The resulting map will establish a baseline for the distribtion of A. snetsingeri to track any future changes. We may also detect one or more Sphodros species that live in the area, and map them, too.

More than 100 sites in the area have already been reported to have purse-webs via the project app, and many more parks and neighborhoods are left to be visited. See the other pages on this website for how to find webs and report your searches.

Current Purse-web Map as of 2022-05-27

The map below shows the Philadelphia region with markers indicating the locations of >220 publicly accessible parks and woodlands that were searched for purse-webs and recorded in the Epicollect project app. Green markers (118 sites) show where webs were found and Red markers (105 sites) where they were not found (20-60 min search). Purse-webs were found at many sites in Delaware and Philadelphia counties, and into adjacent areas of Chester and Montgomery counties. Two purse-web locations west of the main grouping are considered 'outliers' separated from all the others: one is along the Brandywine Creek in Chester County and the other is at French Creek State Park, the only Berks County purse-web sighting. current spider search map Attribution for Maps Data: Google Earth, Image Landsat / Copernicus
The next map is a closer detail that adds a green minimum convex polygon made by connecting the current outermost purse-web sightings, excluding the two western outlier sites. Webs were usually found in under 10 minutes at sites within that range. Circle markers are some of the additional 60+ publicly-accessible park sites identified for a search in 2022. Those sites fill in gaps in the map and test the current boundaries (where webs are not found). Searches in nearby areas of NJ and DE will also look for Sphodros spiders reported in those states. Note that many woodland areas shown on the map are unexplored because they are on private property with NO public access. current spider search map Attribution for Maps Data: Google Earth, Image Landsat / Copernicus
From the data available, and pending species confirmation of the web builders, our Atypus's estimated range is from the Chester Creek valley in western Delaware County east to the Schyulkill River up to Valley Forge, and continuing eastward across the Wissahickon Valley and Tacony/Frankfork Creek parks, to a few sites along Pennypack Creek. Note that some of the Red-marked sites may also have the spiders, but webs were not found during the initial search (20-60 minutes).

Philadelphia's Purse-web Spider ... has a New Twist...

The story of 'Atypus snetsingeri Sarno 1973' (the full species name) begins with strange spiders "found in a swimming pool drain" in Lansdowne, PA, a western suburb of Philadelphia. Some specimens were sent to the late Dr. Bob Snetsinger at Penn State and were subsequently described as a new species in 1973 by his student, Patricia Sarno, who named it in his honor. It's uniqueness as the only species in the genus Atypus on the continent was reconfirmed in 1980 in a Revision of the American Atypidae, where it's relationship to other Atypus spp. was considered; although Pennsylvania is geographically closer to European Atypus species, 'snetsingeri' more-closely resembled an Asian species.

A recent study has determined that the DNA of A. snetsingeri is identical to the east Asian spider, Atypus karschi, so our 'unique' spider actually appears to be an introduced species naturalized to our area, rather than a distinct species. A. karschi is found in eastern China, Taiwan, Japan and South Korea, and probably hitch-hiked with potted plants brought by ship from Asia, perhaps as far back as the late 1700's into mid 1800's. At that time Philadelphia was known throughout the world for its scientists and statesmen, but also for its botanists and gardeners who sought, collected, cataloged and shared plants from around the globe. Your help making the map of our spider's current distribution may help us understand more about when it arrived and how it dispersed through the area.

Map The Spider asks if you can find purse-webs where you live.

Purse-web spiders live a long time and presumably stay in the same tube for many years. The webs are visible, durable, and can be found at any time of the year. Their camouflage is quite excellent and when you find one it's like discovering a secret.

Can you find a purse-web in your neighborhood? at your favorite park? on your next hiking trip? Please let us know by reporting your sightings using the MapTheSpider app. Maybe your search will uncover a new colony of spiders - or even a new species!

* Note: Recent DNA evidence indicates that Atypus snetsingeri is actually an introduced naturalized population of Atypus karschi from east Asia. The name 'snetsingeri' will still be used here until the official synonomy is declared in the World Spider Catalog.

Last Update: 2022-05-28