About 'Map the Spider'

Hi. I'm Steve Tessler, site owner extraordinaire and project leader. Please pardon the awkwardness of the website layout etc. I'm currently typing HTML by hand to update things and barely know what I'm doing! And it shows.

A little history

I've been casually keeping notes on places where I've found the webs since 1975 when I was a student of Dr. Bob Snetsinger at Penn State University and learned about these unique spiders "found only in Delaware County." His Master's student, Pat Sarno, had just published a description of the species two years before - from neighborhoods less than a mile from where I lived at that time! Imagine that. Being from Upper Darby near the Lansdowne site where this spider was 'discovered', I noticed lots of webs in the Darby and Cobbs creek drainages, and I'd look for them when I visited after moving out of the area. I moved back to SE Pennsylvania in 1998 but didn't get more serious about making a real map until 2012 when I found the spiders at Tyler Arboretum, where I have been a volunteer. That was the farthest west that I had found the spider at that time. In 2013 I got a visit from Milan Řezáč from the Czech Republic - an expert on European Atypidae - and showed him around to several sites where I knew the spider occurred and we discussed all that I knew about it. We ultimately collaborated on a paper about the spider that revealed it as an introduced species.

I made a free Epicollect smartphone app in 2015 for my personal use to track and map my searches, and updated it in 2018 to share with others who wanted to help me. I launched this website in September 2019. When the pandemic hit simultaneously with my retirement from the USGS in 2020 I spent more time on the project - scanning satellite and street views on Google Maps to look for new sites to visit that might have webs, and plotting my site visits on Google Earth. Although the area of my search may not seem large, I have spent hundreds of hours driving (think urban traffic) and searching. I decided I had enough data for a good map of the species distribution in the summer of 2023 when visiting sites outside of areas aleady known to have the spider failed to reveal more purse-webs. There are still some places I want to visit, but my project is effectively ended and I am writing it up for publication. I look forward to moving the project information to Wordpress or some other platform so I can easily add more pictures and stop typing everything!

Project Goals

Goal 1: Find out how common purse-web spiders are in the Philadelphia region. As it turns out they are very common. Most people would never notice a purse-web unless they were shown what one looked like and then actually looked for them. Despite their camouflage, purse-webs can be found at any time of year and with a little practice are not hard to spot from a distance. Often many webs are found close together on a tree, a wall or in shrubbery. In the Philadelphia area once you start looking you notice them everywhere.

Goal 2: Determine the range of the PA-local spider Atypus snetsingeri^*. When the project started no one knew that this 'endemic' spider was actually A. karschi introduced from Asia. The current effort suggests that it is limited to southeastern Pennsylvania, from the Chester Creek valley in Delaware County eastward through the Schyulkill and Wissahickon valleys to the Pennypack Creek in Philadelphia and Montgomery Counties, and in adjacent areas of Camden and Gloucester counties across the Delaware River in New Jersey.

Goal 3: Develop non-destructive methods to tell the species apart.. Wandering males of purse-web spider species mostly look different, but otherwise these spiders spend 99.99% of their time within their webs hidden from view. How can we tell who lives in a web without disturbing the spider? One way is to look at the shed skins, or "exuviae," that often get stuck at the top of the purse-web when discarded. The exuviae preserve hard parts and features that could be used to distinguish different species, without digging up or killing any spiders. Indeed, I've found that Atypus karschi can be positively identified by the pattern of spots on the sternum of the shed skin. More on that later. (:

Questions about spiders or webs?

If you have questions about any other spiders and invertebrates you find, including artifacts like webs, check out Bugguide.net or iNaturalist.org. Post a photo and volunteers will help you identify what you found, or just browse the images to see what others are seeing.

You can contact me about this project at

* 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.