I found this immature spider in my garage. At first glance I assumed that it was most likely Steatoda grossa, since Latrodectus variolus tend to be relatively rare in Massachusetts. However, upon closer inspection I noticed the markings on it's back. Steatoda grossa tends to be entirely black on both it's dorsal and ventral sides, but not always. I've also heard that Latrodectus variolus doesn't necessarily have to have only red markings, and can also have white and/or orange markings. I discovered that the spider I found is strikingly similar to the one in this post, which was determined to likely be Latrodectus variolus: https://bugguide.net/node/view/613571.

If this is indeed Steatoda grossa and not Latrodectus variolus, does anybody know how can I properly differentiate between the two?