In the lexicon of entomology, the term true bug identifies a large and important order of tens of thousands of insect species known as the Hemiptera. Hemiptera, the true bugs, are characterized by their sucking mouthparts and incomplete metamorphosis consisting of egg, nymph, and adult stages. Many true bugs are plant feeders, including harlequin bugs, squash bugs, and stink bugs we met in previous episodes, but many are fierce predators playing an important role annihilating pests of crops and ornamental plants. With the arrival of Halloween, Bug of the Week visits three murderous members of the family of true bugs known as Reduviidae, or assassin bugs, which dress in the colors of the season – orange and black.
I bumped into the first of these assassins on the leaves of an herbaceous plant. The milkweed assassin bug, Zelus longipes, has a diabolically clever strategy for catching its prey. Hiding in foliage with its forelegs outstretched, it awaits the approach of an unsuspecting victim. The front legs of this assassin bug are coated with sticky goo (a technical term) perfect for snaring a victim. Once captured, the prey is impaled with a hungry beak that injects proteolytic enzymes, which predigest the contents of the victim. Once that is accomplished, the liquefied contents of the prey are sucked into the digestive tract of the assassin bug with the aid of a tiny muscular pump in the assassin bug’s head.
Black wing buds on the back of the milkweed assassin bug’s back will soon develop into two pairs of jet black wings.
In recent episodes we met blister beetles, ambush bugs, and longhorned beetles feeding and hunting prey on flower heads of goldenrod. Another spooky denizen of goldenrods and other meadow plants is the orange assassin bug, Pselliopus barberi. Why this bug sports a costume of orange with black stripes is known only to Mother Nature and other orange assassin bugs. I watched this stealthy assassin move slowly about a goldenrod blossom with a small leafhopper skewered on its beak. How it was able to sneak up and stab a highly mobile and wary leafhopper is known to the assassin bug but is a mystery to me.
The third amigo in this triad of terror is the large assassin bug known as the wheel bug, Arilus cristatus. We met wheel bugs and learned of their important role as biological control agents of the brown marmorated stink bug in previous episodes of Bug of the Week. In addition to dining on invasive pests, this generalist predator has a taste for native protein sources including several types of caterpillars. To see what I mean, watch the YouTube “Wheel bug stalks caterpillar”, the most watched video in the Bug of the Week ensemble:
In autumn the female wheel bug deposits clusters of barrel-shaped wheel bug eggs on the bark of many types of trees. The following spring when prey return to pester plants, the eggs hatch into gorgeous orange nymphs. The thorax of the nymphs soon changes from orange to black, but as nymphs grow and molt, a reddish-orange color is retained on the abdomen until full adulthood. Like other assassin bugs, the business end of the wheel bug is the powerful beak, or proboscis, stored between the beast’s front legs when it is not in use. Upon spying a tasty morsel, the wheel bug cautiously approaches, embraces the prey with long front legs, and then impales the victim with its powerful beak. The wheel bug pumps strong digestive enzymes through the beak into the prey. These enzymes liquefy the body tissues of the hapless victim. A muscular pump in the head of the bug slurps the liquefied meal up through the beak. As our stretch of unusually warm autumn weather continues, you may have a chance to observe one of these beautiful and deadly assassins prowling about on Halloween’s eve.
Tiny wheel bug nymphs enter the world orange and yellow but soon the head and thorax darken to black. An older nymph impales a hapless lightening bug and skulks to the edge of a leaf to drain the beetle’s blood.
The informative publication “Milkweed assassin bug (suggested common name) scientific name: Zelus longipes Linnaeus (Insecta: Hemiptera: Reduviidae)” by Megha Kalsi and Dakshina R. Seal was used to prepare this episode. Bug of the Week wishes you a happy and safe Halloween.