No. You could say "Jen pomo" (Here is an apple) quite correctly. But "la" is often put before meal names in Esperanto, as it is in many European languages. "La matenmanĝo, la tagmanĝo, etc." It's not essential, but it's customary.
I think you're thinking of Spanish or French. In Latin, "in" means in: "Et lux in tenebris lucet." (Wiktionary tells me that it's actually derived from the Old Latin "en", but Virgil's Latin -- classical Latin -- uses "in."