Subject: Not a black widow, or is it?
Geographic location of the bug: Apartment in eastern Massachusetts
Time: 07:04 PM EDT
I found this odd looking spider in my apartment. My first thought was black widow, given its shape and the pattern on its back, but the coloration is different. What is this spider?
How you want your letter signed: Joe
Though your image is quite blurry, we concur that this does look like a Widow in the genus Latrodectus, and we believe it might be a highly variable Brown Widow, a species recently introduced from Africa. According to BugGuide data, it has been reported from nearby Maryland, and in Southern California in recent years it has nearly supplanted the native Black Widow. While we entertain that possibility, we think this is more likely a harmless member of the Cobweb Spider family, like possibly Steatoda triangulosa which is pictured on BugGuide.
Update: October 22, 2017
Thank you. We’ve gotten a picture of one of these spiders’ underside and observed their behavior a bit. They’re aggressive if their webs are disturbed, and roll into a ball if they fall. The webs themselves are messy and thee-dimensional, but not really funnel shaped.
Does this affect the identification?
We agree with Cesar Crash who provided a comment that this is NOT a Brown Widow, and most likely a harmless Cobweb Spider. Your new image confirms that conclusion.