|Photos by Marty Horowitz 10/24/2016|
What ARE these things? I'm glad you asked. These crystals are the result of Mesquite Girdler Beetles (MGB). The female MGB does this work to protect her eggs. Our favorite bug lady explains (from the link above):
Before she lays her eggs, the female chews a precise, complete circle around a finger-thick twig. This task can take up to two days. She bites all the way through the Xylem and Phloem of the bark and thus disconnects the branch from its water source. Then she chews a separate shallow grove for each of about 8 eggs in the distal, dying part of the branch. The larvae will hatch and live in the wood until they are grown, pupate, go through their metamorphosis and hatch as adult beetles by the end of the next monsoon season to restart the cycle.
The sap collected at her rings in the photos above. Beautiful, isn't it?!
More on this topic here and here.