Just in time for Valentine's Day! What a romantic image this common name conjures up for those who know it not. This slender blackish insect, often with reddish-edged abdomen (depending on the species), gets this name from "kissing" its victim at night, often leaving a reddish bump or blotch on the face. The "kissing" consists of the kissing bug inserting very fine cutting-piercing mouthparts through the skin, then injecting saliva containing an anticoagulant, and finally sucking up a crop full of host blood. Why am I talking about it? It is common where I live and it is medically important. The photo above was taken in August of 2008 of a kissing bug I collected in my washroom. The photo to the left shows the bug upside down in the palm of my hand for scale, and shows the proboscis sheath on the underside of the head. This leathery casing protects the very tiny fine piercing-sucking stylets that do the actual insertion of saliva and taking in of blood.
These are photos of an adult female. The semi-transparent wings visible on the top of the abdomen are found only on adults. Like other insects, kissing bugs go from an egg through various immature stages of growth, here called nymphal instars. Older instars have little wing pads containing the developing wings.
Kissing bugs are so common around my house because we have a high population of pack rats - or wood rats - or trade rats - or white-throated wood rats - take your pick. Scientific name: Neotoma albigula. The wood rat nest is a protected home for the young flightless kissing bug instars, complete with a resident source of blood meals. A blood meal is necessary for each molt into the next size instar; sometimes several blood meals are taken before the current instar grows large enough to molt. There are 5 instar stages before the adult.
Human-kissing bug interaction occurs when the winged adult flies from its wood rat nest home to seek a mate and new territory and a new source for blood meals. Blood is necessary for the male kissing bug to be able to mate and for the female kissing bug to be able to lay eggs. Any warm-blooded animal will do as a source for blood, including wild animals other than wood rats, our pets, and ourselves. Nymphal kissing bugs will also take blood from any mammal, but they are most commonly associated with wood rats.
The winged adults usually begin flying in May where I live, and can be encountered at any time all during the warm months of the year; here that's into October. Adults rest during the day and become active at night. They are attracted to lights, which often brings them to human habitation. Their bodies are very narrow dorso-laterally so they fit into tiny spaces and can enter homes thought to be impervious to insect entry. Once around potential hosts, they use heat-sensing and carbon dioxide sensing receptors to home in on warm bodies exhaling carbon dioxide; scents also attract them. Why do they bite people's faces? Well, often it's because that's the only part of you available to them. Also, that is where there is the highest concentration of carbon dioxide. If you don't wear night clothes and you kick off the covers, there's a good chance you'll get bitten somewhere other than your face.
Usually people never know they've been bitten by a kissing bug. These are really well-adapted parasites. Their slender little tarsi can hardly be felt when they're walking on human skin, and they are very light-bodied before they engorge with their blood meal. The fine little stylets usually can't be felt entering your skin; some people say they felt a little tickle but not pain. The itchy pinkish bump at the bite site (and some people don't even have this reaction) can be attributed to lots of other things. So why are they medically important?
It's your body's reaction to the proteins in the kissing bug's saliva that usually causes the most harm. Our immune system reacts to the foreign protein and allergic responses can result, ranging all the way from moderate discomfort to feeling really ill to life-threatening anaphylactic shock. It's gotten to the point where I get really sick if one bites me. I get hives all over, a fever, nausea, and fatigue. It takes me several days to recover. Needless to say, I devise methods to avoid being bitten. What's worked best over the years has been to keep a light burning in a part of the house distant from my bedroom. During kissing bug season, I do "bug patrol" before I go to bed; I look through the whole house and inspect all around the light source (walls, furniture, floor, lamp shade, ceiling, etc.) for kissing bugs, and I crush them to death and dispose of them without touching them with my bare skin. Why later. I leave the light on, and if I have to get up in the night during kissing bug season, I check again. One of my friends went so far as to place a piece of dry ice (carbon dioxide) by the light source as a further attractant to kissing bugs. I also keep cats. They help to keep down the wood rat population in and around my house, and thereby also really close kissing bug infestations. However, the desert surrounds my house and there are gazillions of wood rats out there with their messy nests in prickly pear patches, constant sources of winged adults. We have lots of natural predators: bobcats, coyotes, Harris Hawks, gopher snakes, king snakes, rattlesnakes, but those wood rats just keep coming. There's a reason rodents are an important element of the food chain!
There's another factor making kissing bugs medically important. They are carriers of a protozoan parasite, a trypanosome that causes a terrible malady called "Chagas' Disease." This is common throughout Mexico, Central and South America, and it is transmitted by species of kissing bugs native to those areas. Wild animals which are reservoirs of the disease are usually rats but could also be bats, armadillo, mice, squirrels, raccoons, etc. that the kissing bugs feed on. They take in the parasite with the blood meals; the trypanosomes grow in the hindgut of the insects. When they bite a new host, the more southern species of kissing bugs usually defecate after they take in the blood. The fecal material, containing parasites, then can get scratched into the bite site, and the trypanosomes can infect the blood and body of the new host. Thank goodness our species of kissing bugs tend to defecate after they've flown off. There have been studies showing that Chagas' Disease is resident in a percentage of rodents in the southern and southwestern United States, and that a percentageof kissing bugs sampled in these areas contained the trypanosomes of Chagas' Disease in their gut. So--don't touch crushed insects with your bare hands or skin, because if there's a lesion or break in the skin, or if you touch mucous membranes and trypanosomes are present, you run the risk of inoculating yourself with a very bad parasite.
I'll end with a horror story involving kissing bug nymphal instars. I was part of the audience in an older building which was being used for giving slide shows during the day, so the room was periodically darkened for at least 45 minutes. The attic of this old building had been home to innumerable generations of wood rats. Unknown to anyone, some cracks had developed in one area of the ceiling. Also unknown at the time, but found out later, was that the resident wood rats had recently been screened out by placing fine mesh wire over all possible points of entry. So--there were a lot of VERY hungry nymphal kissing bugs in that attic, and it was dark, signalling a time for activity, and they could sense heat and carbon dioxide below. Unfortunately, some of them found their way through those little cracks and through the holes in the acoustic tiles and they dropped down onto the friend sitting beside me. She began to complain of feeling itchy, and then asked if there could be mosquitoes in the room. Finally we both went outside to see if we could find the source of her discomfort. She was horrified when fully engorged nymphal kissing bugs (they look like really fat leathery black ovoid ticks) began dropping from her clothes and falling onto the ground. Arggghhh! Call in the exterminators.
Here's hoping you have truly pleasant and enjoyable kissing experiences on Valentine's Day. And, if you are a winter vistor to Arizona, you can relax in knowing that you are here outside of kissing bug season. Please visit my blog site again; I'm going to aim for weekly postings.
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