The mason wasp (Monobia quadridens) is stunning in appearance and less harmful than other varieties of wasps, bees, hornets and yellow jackets. The mason wasp–also known as the potter wasp–is so named because it likes to tunnel into the mortar between bricks and its nest often resembles tiny clay urns. Discerning mason wasps from other kinds of wasps or flying insects is easy, if you know what to look for. Usually, the mason wasp's bold markings are a dead giveaway.
Look for mason wasps in wood borings or burrows in dirt banks. Mason wasps also take over abandoned carpenter bee or ground bee nests.
Identify a mason wasp nest by looking for dead caterpillars or parts of caterpillars and cells separated with mud partitions in the nest. In addition to caterpillars, mason wasp nests may also contain other prey, such as cutworms, cabbage loopers, armyworms and beetle larvae.
Study the insect’s physical characteristics. Mason wasps are approximately 20 mm (slightly less than 1 inch) long and black with bold, yellow-white stripes and markings. In some species, the markings can also be orange or red. Males have a yellowish pentagonal spot on their face.
Look for tunnels in the mortar between the bricks on the outside of your house or other structure. If you see winged insects resembling wasps inside or going into and out of these tunnels, the insects are likely mason wasps.
Spot mason wasps by their behavior. Unlike other kinds of wasps, hornets and yellow jackets, the mason wasp is a solitary insect, meaning it doesn’t form colonies. Mason wasps are not aggressive and won’t protect their nests.
You’ll often see mason wasps feeding on the nectar of flowers. They are great pollinators in the absence of bees.
Spot a mason wasp quickly by looking for its long, bluish-black wings and bold markings. Use a magnifying glass to study the mason wasp more closely for better identification.
Don’t try to kill the mason wasps or destroy their nests. Mason wasps rarely compromise a building’s structure when tunneling into the mortar. When the mason wasps abandon the nest they’ve built near the mortar, you can simply scrape it off.