Found this brown Spider in my garage and was really curious about what kind it was. It moves really fast and stops when it is blocked by a brightly colored object.
Giant House Spider, Eratigena duellica or saeva.
Is saeva still in use?
Yes, what happened is duellica, saeva, and atrica were synonimized in 2013 … then DNA analysis was done showing them to be three distinct species after all (see “Oxford & Bolzern, 2018). It was also shown that in some places there is potential for hybridization between saeva and duellica, sometimes I leave them at genus for this reason.
Oh that’s interesting! So is genetics the only known way to distinguish them?
There are morphological differences. I can make an educated guess based on location and subtle differences in the patterns. I have an idea how to distinguish saeva from duellica but it’s based on only one I saw IDed as saeva on the British Arachnological Society site, I don’t know if it’s reliable… so if I see that variation in areas where the species might overlap I’m inclined to file those to genus rather than to species … atrica is a little easier to distinguish … close examination of the genitalia can differentiate them with more certainty.
Very interesting! Thank you!