CREATE TABLE table_906 ("No. in series" TEXT, "No. in season" TEXT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Storyboarded by" TEXT, "Original air date" TEXT, "Production code" TEXT)

On what date did the episode with a series number 31, with a story written by William Reiss, air for the first time?
SELECT "Original air date" FROM table_906 WHERE "Storyboarded by" = 'William Reiss' AND "No. in series" = '31'
SELECT "Original air date" FROM "table_906" WHERE "No. in series" = '31' AND "Storyboarded by" = 'William Reiss'