https://phys.org/news/2018-10-sand-flies-marijuana.html

To learn more about what sand flies eat, the researchers captured specimens in Brazil, Ethiopia, Kazakhstan, Israel and Palestine. They removed the gut contents from each specimen and subjected them to DNA analysis to determine which plants it had come from.

In looking at the plant types that the flies ate from, the researchers found that Cannabis sativa was the most popular—they found it in flies from four out of the five locations studied. This was intriguing because marijuana plants are extremely rare in three out of those four regions due to its cultivation and illegality. The researchers suggest this indicates the sand flies have a particularly strong affinity for the plants—so much so that they actively seek them out.