Assassin bugs (family Reduviidae) are widespread, highly effective predators. With over 7,000 species globally, these true bugs are characterized by a narrow head, a distinct neck-like structure, and a formidable, three-segmented proboscis. They are primarily generalist hunters, using their specialized mouthpart to pierce the exoskeleton of other insects and inject potent, liquefying venom. Despite their predatory efficiency, they serve as a food source for larger animals.
Vertebrate Predators
Larger, opportunistic insectivores often overcome the assassin bug’s defenses through sheer size and speed. General groups like insectivorous birds, reptiles, and small mammals prey on the Reduviidae family. Birds, such as shrikes and flycatchers, use quick, precise attacks to seize the insect and prevent the defensive strike of the bug’s proboscis.
Ground-dwelling predators, including lizards and small rodents like shrews, overwhelm the bug with a swift bite to the head or thorax, neutralizing the threat of its venomous stab. Bats, as nocturnal hunters, opportunistically consume flying adult assassin bugs. They rely on echolocation and speed to capture the insects mid-flight before they can react defensively. A defensive bite from a large species, such as a wheel bug, can be painful and deter future attempts.
Invertebrate Predators and Parasites
Assassin bugs are also preyed upon by other invertebrates. Large web-building spiders can trap flying adult assassin bugs, immobilizing them with silk before the bug can use its piercing proboscis. Conversely, some specialized assassin bugs, like the thread-legged bug (Stenolemus), have evolved to prey on web-building spiders by plucking the silk to mimic trapped prey.
Praying mantises, which are ambush predators, pose a threat, especially when they are significantly larger than the bug. Their powerful, raptorial forelegs quickly grasp and crush the assassin bug, preventing a defensive venomous injection. The Reduviidae family is also susceptible to parasitic threats that complete their life cycle inside the bug’s body.
Specific parasitoids, such as Tachinid flies, target true bugs. These flies lay their eggs on or near the assassin bug, and the resulting larvae burrow inside to feed on the host’s internal tissues. The larva feeds on non-vital tissues first, allowing the assassin bug to remain alive until the larva is ready to pupate, which ultimately kills the host.
Defense Mechanisms That Limit Predation
The potent defense mechanisms assassin bugs possess limit the number of successful predators. The most well-known defense is the ability to deliver a painful, venomous bite with their robust proboscis when handled or threatened. Some species, such as Pristhesancus plagipennis, produce two chemically distinct venoms: one for subduing prey and a separate one specifically for deterring predators.
Many assassin bugs employ chemical defenses, releasing a foul-smelling odor when disturbed that makes them unappetizing to attackers. Other species, like the milkweed assassin bug, secrete a sticky, viscous substance on their legs that can ensnare small attackers.
Passive defenses include cryptic coloration, where their bodies blend seamlessly with bark, leaves, or soil, making them difficult for visual hunters to spot. Certain nymphs, such as the masked hunter, actively cover their bodies with debris or the remains of dead prey, creating camouflaged armor to deter predators.