from Why We Eat What We Eat, p. 35:
The list of insects eaten in Mexico then and now is awesomely long. Water bugs (moscos de pajaro, axayacatl) whose eggs (ahuautli) are still gathered in the same manner described by Sahagun: Bundles of reeds that are stuck upright in the muck in shallow water attract the moscos, which lay eggs on them. After a month of this, people "harvest" the bundles, dry them out, and shake the eggs onto cotton sheets. Sahagun says they were then eaten in tamales and tortillas. Today, according to Castello Yturbide, they are toasted, ground up, and made into little cakes held together with turkey egg. This is a documentable survival of a dish that goes back at least to 1798 when, according to Manuel Orozco y Berra...these apparently humble concoctions were a garnish for the festive dish called revoltijo, served on Christmas Eve and at the vigil on Thursday night of Holy Week. "The taste," he wrote cryptically, "is like caviar but not so tasty."