Making an exhibition of himself

Jon awoke to find himself lying flat on his back stark naked. Groaning he sat up and looked around to see that he was in a field of tall grass. Except this was a field that had walls on three sides painted to look like an extension of the field and on the fourth had a wall of glass. Beyond it was a crowd of spider aliens and behind them he glimpsed other enclosures which he guessed contained other aliens. A groan next to him and he looked down to see next to him lay the naked body of...