You may see the evidence of Leaf Cutter bees in your yard, the distinct half circles taken out of soft leaves. Leaf cutters are active in warmer temps and carry cut leaves to construct their nests nearby.
These bees are solitary or non-social bees, meaning they do not form hives and each bee assumes the role of both queen and worker. Leafcutter bees are not aggressive and have a very mild sting that is used only when they are handled. They are relatively harmlessness to humans.
They are great pollinators and carry pollen on their underbellies, pollinating 95 out of every 100 flowers they visit. Pollen is more likely to stick to the next flower they land on carried in this way.
Leaf cutter bees prefer soft tender leaves and often new growth. Japanese Blueberry, Chinese Pistache, and Ash trees are commonly affected by Leaf cutters in the Southwest.
While you may worry about the impact on your plants, you may be relieved to hear they usually do not remove enough leaf tissue to cause damage to plants. In fact, attempts to eliminate leaf cutter bees from your yard is discouraged due to the limited damage they cause and that insecticides are generally not effective as they do not eat the leaves they cut. In conclusion, you should probably just let them beeee.