Assassin Bug

It is camouflage and armour rolled into one. The nymphs of certain assassin bugs, best studied in the African and Asian genus Acanthaspis, have a coating of fine sticky hairs and a waxy secretion on the abdomen, and after draining a prey insect — often an ant — they use their hind legs to pile the empty husk onto their back. Over time a nymph builds up a wobbling heap of ant carcasses, dust, sand, and plant fragments many times the size of its own body. Experiments have shown this "backpack" hides the bug's outline and, crucially, its scent from its own predators, especially jumping spiders, which are far less likely to attack a bug wearing a mound of dead ants than a bare one. If the pile is knocked off, the bug builds a new one. The bundle also works as a decoy shield that a predator grabs instead of the bug.

Two situations. First, any large predatory assassin bug, such as a wheel bug or a milkweed assassin bug, will jab defensively with its rostrum if picked up or trapped against skin, and the bite is genuinely painful — often compared to a hornet sting, with burning, swelling, and sometimes numbness that can last for days, though it is not medically serious for most people. Second, the blood-feeding kissing bugs (subfamily Triatominae) deliberately bite sleeping people to feed, usually painlessly, around the lips and eyes (hence "kissing bug"). That bite itself is minor; the danger is what the bug leaves behind.

Chagas disease is a potentially life-threatening infection caused by the single-celled parasite Trypanosoma cruzi, and it is spread mainly by kissing bugs in Mexico, Central America, and South America, where an estimated six to seven million people are infected. The bug picks up the parasite by feeding on an infected animal or person. When it later bites a new host, it feeds and then defecates on the skin nearby; the parasite is in the faeces, and it enters the body when the person unknowingly scratches it into the bite wound or rubs it into the eyes or mouth. Early infection is often mild or unnoticed, but decades later around a third of infected people develop serious, sometimes fatal heart or digestive-tract damage. Improved housing, insecticide spraying, and bed nets are the main controls.

Very. The great majority of the roughly 7,000 assassin bug species are pure predators of other invertebrates, and several are important natural enemies of crop and garden pests, taking aphids, caterpillars, leafhoppers, beetle larvae, and flies. Gardeners who recognise species such as the wheel bug or the spined assassin bug are generally advised to leave them alone and let them work, while simply not handling them because of the painful defensive bite. Some assassin bugs are even reared and sold commercially for biological pest control in greenhouses. The bugs are ambush or stalking hunters and hunt by day and night depending on the species.