UPDATE: PROJECT DATA COLLECTION IS COMPLETE.
SEE THE MAP BELOW!More than 250 parks and woodlands in the Philadelphia region were visited to search for purse-webs, and they are much more common than anyone had thought. Thank you to the volunteer web hunters who submitted sightings via the smartphone app: HeatherS, JohnWG, TomB, Elenor (MA), BernardB, BruceT, LJB, LaurenH, GrantDB, 'Julie' and MB.
Please report any *new* purse-web sightings using Bugguide.net or iNaturalist.org.
Note: DNA evidence published in 2022 indicates that the Delaware County, PA, spider formerly known as Atypus snetsingeri is actually an introduced naturalized population of Atypus karschi from east Asia. The name 'snetsingeri' is now considered a junior synonym of A. karschi in the World Spider Catalog.
Purse-web mapping project results, 2015-2023 ( as of 7/1/2023)
Southeastern Pennsylvania and Adjacent States.
The map below shows the Philadelphia region with markers indicating the locations of 256 publicly-accessible parks and woodlands that were visited between 2015 and 2023. Searches for purse-webs at each site typically ranged from 1 minute (found immediately) to 20 minutes, although some sites were searched longer.
Green markers (114 unique sites) indicate locations where vertical purse-webs were found and Red markers (142 sites) are searched places where they were not found .
Attribution for Maps Data: Google Earth, Image Landsat / CopernicusPennsylvania: Purse-webs were found at many sites in Delaware and Philadelphia counties, and into adjacent areas of Chester and Montgomery counties. Heavily urbanized sections of south Philadelphia are mostly impervious surfaces with few parks and little exposed soil, and were not searched. One isolated colony of purse-web spiders, confirmed as A. karschi, was located in a wooded preserve along the Brandywine River in Chester County far from other web sites, and extensive searches nearby did not reveal other colonies. One sighting of a vertical purse-web was recorded (photographed) in French Creek State Park, the only Berks County purse-web seen in the project, and multiple repeat visits to the site and surrounding areas did not reveal any more webs; that purse-web spider species remains undetermined. Searches of several wooded parklands in Lancaster and Bucks counties, west and east of Philadelphia, respectively, did not reveal purse-webs.
New Jersey: In 2022 and 2023 searches were made at 27 sites in four PA-adjacent New Jersey counties across the Delaware River from Delaware county and historic Philadelphia. Purse-webs were found at 7 wooded sites in Camden and Gloucestor counties within 6 miles of the Delaware River. Webs of the American purse-web spider Sphodros rufipes (confirmed from excavation/identification) were found in Rancocas State Park near a reported sighting of a male spider reported on iNaturalist.
Delaware and Maryland: A few wooded parks in New Castle County, Delaware (adjacent to Delaware County, Pennsylvania) were searched but no purse-webs were found. One unplanned and unsuccessful site visit/search was done in a Maryland forest near the Coniwingo Dam far from known purse-web sites.
Estimated USA Range of Atypus karschi as of 2023-07-01
The map below shows 22 sites (yellow dots) where purse-webs were found and the spiders were excavated and positively identified as Atypus karschi. The green polygon connects the outermost sites of the main grouping (see above map) and, along with the outlier site in the Brandywine valley, is the actual known distribution of A. karschi in the region. Excluding the single outlier colony, the blue circle with a diameter of 30 miles (48 km) roughly describes the current range. This introduced spider species is now confirmed from six counties, four in Pennsylvania (Delaware, Chester, Philadelphia and Montgomery) and two in New Jersey (Camden and Gloucester). Purse-webs were very easy to find at many sites within that area.
Attribution for Maps Data: Google Earth, Image Landsat / Copernicus