Hi Wolfram,
I've been looking through my pics of female
S. lineolata, but none are as clear as yours when cropped close-up. Also you have captured that one in good lighting, which shows the detail of the skin up very well. I think what we are seeing here are sensory pores.
Here's a bad pic of one of my females:
And closer:
I can make out little bumps under the skin. Not as pronounced as the tubercles seen on the males.
Emma