Believe or not, this question has come up before... :) Some catalogs (but not all) list two species of Leucauge in North America, but no one has been able to find a definitive ID for the L. mabelae (it seems to only be tropical). So, I believe all of the Leucauge have been condensed to a single species, until we discover otherwise.

Here's the small discussion thread from the summer...

The M. gibberosa can resemble a L. venusta in coloration, but they are not the same spider, and the M. gibberosa is not commonly referred to as an orchard spider. :) The M. gibberosa has slightly different marking pattern (very subtle) and has very distinct spines (setae) on the legs. The L. venusta has smooth legs, and darker leg joints with greener mid-sections between the joints. (This is a good way to rule out M. gibberosa.)

M. gibberosa

I moticed that about the spines...That is why I did not think it was M. gibberosa.
Anyway, there are gazillions of them down here, I should have ID'ed them long ago.

the legs on these are much longer than the gibberosa.

I am not so sure about that. This individual had the red/orange spots on the opisthosoma typical of Leucauge. I will post another, crappier image.