More than 100 species of assassin bugs (members of the family Reduviidae) are found across North America. The best-known are the spined assassin, the masked hunter, wheel bugs, and members of the genus Zelus. Adults can be 3/4 inch or more in length.
The weapon of choice of adult assassin bugs is a sharp, curved, daggerlike mouthpart that they keep tucked under their body until it’s time to go to work. Assassins use their bristly front legs to ambush and capture prey, which they then pierce with their “sword” and inject with a lethal toxin, killing the prey within seconds. The toxin liquefies the unlucky captive’s innards in short order and the assassin slurps them up like a protein shake, leaving only the empty exoskeleton behind.
It might sound a bit gross until you consider what assassin bugs consume. Common prey includes garden nasties such as hornworms, Mexican bean beetles, Colorado potato beetles, leafhoppers, cucumber beetles, lygus bugs, aphids, and caterpillars of all sorts. These predators aren’t overly discriminating and will capture a beneficial lady beetle or two along the way, but overall they’re on the right team, working to control pests in any landscape that isn’t regularly blanketed with chemical pesticides.
Most assassin bugs are brown, green, or black; a few species display brighter colors. They have broad bodies, elongated heads, and long, spindly legs. Females lay eggs in cracks and crevices. After hatching, the insects pass through several nymphal stages before fully maturing. Assassins can overwinter as nymphs or adults.
Assassin bugs are covert operators and aren’t encountered by gardeners on a regular basis. At most, you might come across one or two each season. This is a good thing, though, because an accidental encounter could result in a nasty welt: That knifelike mouthpart also works on human flesh.