create a npc_antlion and a npc_antlion_template_maker.
Set up the antlion however you want it and give it a name, make sure the "Template NPC" flag is checked. Set up the npc_antlion_template_maker however you like, but I recommend using info_node_hints with a group name as spawn points, and then putting in the name of this group into the spawn on hintgroup value in the template maker.
To actually spawn the antlions, you have a few options. You could set the template_maker to always be on, and then set the flags in the template maker so that the antlions spawn nearest to the player, or you could trigger the template_maker to turn on as soon as the player passes through a trigger_multiple brush entity. You could even do it like they did on sandtraps and set an env_player_surface_trigger to turn on the template maker every time the player steps on a sand texture and turn off the template maker every time the player gets off the sand texture.
