My grandfather was a rural mail carrier for many years. He loved his job. Well, he loved his job except for one aspect – the spiders. I’m sure more than one spider lost its life at my Pop’s hands.
I’m guessing he didn’t realize all the good things spiders do.
For instance, spiders like the Golden Garden Spider 
(shown in the photo at the PPL Wetland conservation easement), arigope aurantia, eat insects. This helps maintain populations of pests like mosquitoes. Maintaining lower levels of mosquitoes can help keep diseases, like West Nile Virus, from spreading.
Spider venom is also being studied for use in medicine. Medical researchers are looking at whether specific peptides in some species’ venom could be used with heart attack and stroke patients to lessen damage to the heart and other muscles. Other researchers are looking at peptides that may help with neuro-muscular conditions.
Spiders also help scientists like Dr. Brian Mangan, King’s College. Dr. Mangan is studying the pathways of mercury in the aquatic and terrestrial food chains and the Spined Micrathena is helping him do this.
Small insects ingest mercury from a number of sources in their environment. The Spined Micrathena then ingests the small insects after trapping them in its web (it’s a pretty impressive web) and the mercury from their prey accumulates in the spider’s body.
Dr. Mangan has documented mercury is present in the spiders and has noted higher levels in spiders near coal-fired power plants that release mercury to the environment. He’s also working to compare mercury levels between riparian and upland areas to see if mercury is leaving rivers like the Susquehanna in the bodies of aquatic insects that fly from the river and are perhaps captured in spiders webs. By capturing Spined Micrathenas from both areas and comparing the mercury levels between the two groups he can see if spiders that tend to eat bugs near the river have more mercury in their bodies.
If you want to learn more about spiders in Pennsylvania, visit Penn State Extension. They have information on “Spiders Commonly Encountered in Pennsylvania and the Northeast” (http://ento.psu.edu/extension/factsheets/commonly-encountered-pennsylvania-spiders).