Antlion Burrows

Antlion Burrows are structures randomly found in the main Desert, where the Underground Desert is beneath. There is has a 1/3 chance to generate one of four types of structures that usually lead to the Underground Desert. They are referred to in the code as Chambers, Anthills Larva Hole and Pit:
 * The Chambers consist of of a zigzagging downward tunnel with one or two small rooms connected to the corners.
 * Anthills and Larva Holes are respectively upward cones and downward funnels with narrow holes. Each generate as two or three on the main desert.

Prior to 1.4, the desert always generated with a large pit entrance.