How does Federico Garcia Lorca use imagery in Gacela of the Dark Death?

In Stanza Four the speaker requests to be wrapped in a veil that will protect him from dawn's fistfuls of ants, and sprinkled with "agua dura" (hard water) to protect him from dawn's "scorpion's sting." This imagery is particularly mysterious, since it is difficult to see how a veil will protect the speaker from ants or how water will protect him from a scorpion.