Hello,

You could use small arthropod species (for example collembolans) and also immature arthropods (for example immature crickets). You can also use articifial diets to rear the individuals. Please find attached some references which might be useful.

http://www.americanarachnology.org/joa_free/joa_v20_n3/joa_v20_p207.pdf

http://www.researchgate.net/publication/232679528_COMPARISON_OF_THE_SURVIVAL_OF_THREE_SPECIES_OF_SAC_SPIDERS_ON_NATURAL_AND_ARTIFICIAL_DIETS/file/50463520d4c7f6f187.pdf

You can also find a chapter about this written by D.Amalin in the last edition of the ecophysiology of spiders book.

Hope this helps!

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Depending on the instar, I have been successful  feeding them flightless Drosophila.