During the summer months, if the area beneath a desert tree is well-lit and against a dark background, you may see a fine mist falling from the tree. I see this phenomenon sometimes when I conduct tours at the Arizona-Sonora Desert Museum. When I do, I gather the people beneath the tree to experience the mild evaporative cooling. Then I tell them what the mist is: bug pee.
The mist is produced by bugs called sharpshooters (aka leafhoppers). There are many species and the bugs range from one-quarter to one-half inch long. The bug in the photo (courtesy of the Arizona-Sonora Desert Museum) is the Smoke Tree Sharpshooter.
You can see more photos at BugGuide and from a University of Florida article. The latter reference also gives the natural history of this bug.
“The diet of the majority of sharpshooters consists exclusively of nutrient-poor xylem fluid from a great variety of plant species. This fluid is comprised of over 95% water with small amounts of organic and inorganic molecules.” After extracting the nutrients, sharpshooters excrete most of the water. That’s what produces the mist.
To successfully develop and reproduce by feeding solely on nutritionally poor xylem fluid, sharpshooters have high consumption rates coupled with an efficient digestive tract that features a re-circulating loop called a filter chamber. They are extremely efficient at assimilating what they have ingested and their waste is 99% water with small amounts of ammonia.”
Sharpshooters have good eyesight and will try to hide by moving around a tree branch if you approach them. Sharpshooters have powerful hind legs which allows them to perform long jumps. They also have two pairs of wings and are strong flyers. Their flying prowess allows them to fly long distances and visit many plants. And that sometimes presents a problem.
Some sharpshooters are vectors for viruses, bacteria, and other microorganisms that attack plants. Here are some articles about that aspect:
A New Sharpshooter Threatens Both Crops and Ornamentals
Sharpshooters are preyed upon by mantids, dragonflies, spiders, and wasps.
Look for the mist of the sharpshooters when you are outside this summer.
See also ADI articles on other desert critters:
Venomous Centipedes and Cyanide-Oozing Millipedes