Amazing Assassins

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Published on: Jun. 2, 2003

Last revision: Nov. 15, 2010

may vomit and faint.

One bite you should definitely avoid is that of the blood-sucking conenose. Two species occur in Missouri: Triatoma sanguisuga and T. lecticularia. These are kissing bugs in the truest sense, sometimes drawing bloodmeals painlessly from the faces of sleeping humans. An inch long, oval, and very flat, they are easily recognized but seldom seen. They live and breed in the nests of wood rats, their normal hosts. Instead of the normal five nymphal stages, conenoses have eight, and can take up to three years to mature. They require at least one bloodmeal (usually several) to graduate from one stage to the next. Adults fly only briefly, to find mates and disperse, at which time they are attracted to lights.

From Mexico to Argentina, Triatoma and its relatives rank among the deadliest of insects. They frequently carry Chagas' disease, caused by a one-celled organism similar to the one responsible for African sleeping sickness. Armadillos and possums are common reservoirs of this pathogen. Oddly, the conenose does not transmit the parasite in the course of feeding, but when it defecates, expelling the microbes in the vicinity of the bite. Victims infect themselves when they scratch the feces into the wound, or then touch their eyes or other mucous membranes with contaminated fingers.

A quirk in the behavior of U.S. Triatoma helps explain the absence of Chagas' here. Our species leave their victims before excreting wastes. If only the others could be toilet trained! Chagas' afflicts an estimated 7 million people annually, of which 10 percent may die. The highest incidence is among the rural poor who sleep in thatched-roof huts among their domestic livestock.

A "normal" conenose bite usually leaves a welt or fat lip the following morning. Itching, burning, redness and blistering are not uncommon. Serious side effects can include heart palpitations, nausea, faintness and shortness of breath.

Unfortunately, Chagas' disease is subtler in its initial manifestations. A one sided swelling of the face or eyelids, followed by fevers, may be the only symptoms. Most victims are unaware of their infection for 10, or even 20 years. By then, irreparable lesions have developed in the nervous system, heart and digestive tract. Some say Charles Darwin contracted the disease during his epic voyage on the HMS Beagle, eventually succumbing to it years later.

Avoiding our harmful assassins involves taking simple precautions. Exclude them from your home by repairing window screens, applying weatherstripping, and sealing other openings. Use yellow bulbs in porchlights, and dispense with bug zappers. Do not camp or sleep inside caves, barns or other sheltered areas frequented by masked hunters, corsairs, and conenoses. To avoid a self-defense bite, gently brush away any bug that lands on you.

The beneficial qualities of assassin bugs far outweigh their negative potential, and learning to get along with these indispensable predators is in our own best interest.

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