Nature's Assassins: Assassin Bugs

What a great name!! – “Assassin Bugs” – and these critters really do try to live up to it, by jabbing their sharp mouth into other insects they’ve captured, and sucking out the juicy stuff inside. In this effort these insects certainly qualify as “beneficial” predators. Unfortunately some of the different kinds are also given other names, and these are far more threatening to us. We call some species Kissing Bugs or Cone-nosed Bugs, because there are a few kinds that feed on the blood of animals rather than on other insects. This interesting family called the Reduviidae is worth knowing about, and worth being aware of if you live in areas where the kissing bugs are prevalent.

Let’s get this bad part over with first. In North America we do have a number of species of kissing bugs that feed on the blood of mammals, and we at least need to be aware of them. These blood feeders are in the insect genus Triatoma, and we have up to twelve species in the U.S. Some are so adapted to feeding on human blood that in Central and South America they may never leave the homes in those areas, staying in the crevices and other hiding places afforded by poorly constructed homes. In Latin America, in particular, many homes are built with available wood and thatch roofs, and there are abundant hiding places for the bugs to get into where they are not seen. In the U.S. this is possible as well, but more often the Triatoma lives outdoors and feeds on other kinds of animals. For a more detailed look at the blood-feeding assassin bugs please take the opportunity to read another BugInfo article on “Kissing Bugs”. They can be of very high importance to our health due to their ability to transmit a disease called Chagas Disease, which so far still may be restricted to Latin America, and not spread by the bugs in the United States.

In the U.S. we are relatively free of this terrible disease, even though kissing bugs in the U.S. have been found infected with the pathogen. We still do not want to be bitten by these creatures though, as their saliva can cause a variety of reactions in people, ranging from not much at all to potentially life-threatening allergic responses in sensitive people. The more often you are bitten the more of a reaction you may experience, and it could be as serious as swollen tongue, larynx, and trachea and serious difficulty in breathing. More commonly the bite would leave a welt or reddened area of the skin that itched or felt warm to the touch. Some studies indicate that about 7% of people may have that much more serious reaction, even leading to anaphylactic shock, that could come on immediately after the bite, and if you believe you have been bitten by an assassin bug you should consider seeking medical help.

These are not insects to obsess about in the United States, but simply be aware of them, know what they look like, and if you have large numbers around your home learn about their behavior and likely sources so you can eliminate them. Most kinds are beneficial for us, and the risk of being bitten is minimal. One kind, called the Masked Hunter, is even a predator that feeds on Bedbugs, and may be found indoors in homes where these insects are living. The Bedbug has become a much, much more common problem in homes in North America, and this could increase the chances for the Masked Hunter to be there as well. This assassin bug is not a blood feeder, but there could be that unfortunate encounter where someone could be bitten. The assassin bugs often live in the nests of wild animals, such as wood rats or ground squirrels, so if these are near your home they should be managed in some way.

Pest Exclusion:

It is not our goal to eliminate all bugs from the landscape, but only to keep them out of the home. For larger insects like assassin bugs this can be accomplished by making that very thorough inspection of the outside of your home to identify all the possible openings available for bugs and other animals to enter. Any and all openings should be closed permanently with the appropriate material, such as caulking, weather-stripping, wood, metal flashing, expanding foam aerosols, or some other material. You will be amazed at the holes and gaps you can find once you take that critical look at your own home, and working a little bit at a time you can seal them off. The benefit from this goes way beyond just keeping assassin bugs out. You keep out the many other bugs that look at your home as their winter quarters, you keep out bats, you keep out birds, and you expel rats and mice. We can love wildlife, but we may not want to live too intimately with it.

Most assassin bugs are just predators on other bugs, and with their “raptorial” front legs they grab onto a small bug and hold it against the front of their body. They then quickly insert their proboscis, or feeding beak, and suck up the internal fluids of that other bug. One large assassin bug found in the western U.S. is called the Two Spotted Corsair, identified by the bright yellow spot on each wing. At rest these insects hold their wings flat over the abdomen so that it looks like a single yellow spot. They may come to lights, and if mishandled or if trapped in clothing it can give a painful bite. This species makes its living by feeding on other insects, so even though it could bite humans it does so only in self defense, and otherwise should be considered as a desirable insect to have in the garden.

The mouth of an assassin bug is an amazing weapon, shaped like a stout, curved spike that it can plunge down and into the body of its victim. While not in use this “proboscis’ is held beneath the body and pointing backward, but once food is in hand the insect extends it slightly forward and jabs its prey. The saliva of the insect feeder assassin bugs is a nice mix of enzymes that can dissolve the innards of other insects, and once liquefied these tasty juices are then sucked back out much the way we might enjoy a milkshake. Any parts left over are simply discarded. The saliva also has the ability to paralyze and immobilize the food prey, allowing the assassin bug to more thoroughly enjoy its meal without the need to hold on so tightly.

In the eastern U.S. you may find one of the largest assassin bugs, and that is the distinctive species called the Wheel Bug. It gets its name from the knobbed “cogwheel” crest that arises over its thorax. It is so large that it is even capable of feeding on the large “horntail” caterpillars that eat your tomato plants. Some of these larger kinds, when upset in some way, will give off an audible squeaking sound by rubbing body parts together. While the adult wheel bugs can feed on very large insects, the small nymph stages may choose to go for smaller soft-bodied foods, such as aphids on your plants. Thus, like the 2-spotted corsair, this insect should be judged favorably – although respected – when found in our gardens. Just exactly what that knobby structure on top of the bug is there for is not known, although it could function in mate recognition, or possibly simply serve as a visible warning to its own predators that this is a foul-tasting insect. Due to its close relationship to other true “bugs” such as Stink Bugs, the assassin bugs will usually be endowed with body fluids that taste pretty nasty, a fact quickly recognized by predators that attempt to eat them.

Other varieties of Assassin Bugs may be much smaller and less visible, such as the Leafhopper Assassin pictured here. This thin-bodied, slow-moving insect wanders over your garden plants in search of its own preferred foods, often more of the plant feeders such as the hoppers, scales, or aphids. You may not even see the assassin bugs due to their camouflage coloring, or because of the bits of debris that stick to the bodies of the immature bugs, which have a sticky coating on them just for this purpose. As with the others discussed in this article this bug is capable of biting, does so only when it feels directly threatened, and does not feed on blood or present any particular health concern.

There are many other varieties of assassin bugs, as well as a number of other “bugs” in the group we call the “True Bugs” that also are predators and parasites on other insects. We have damsel bugs, ambush bugs, and pirate bugs on the land, and water boatmen, backswimmers, water striders, water scorpions, and giant water bugs in aquatic settings. These beneficial bug-eaters help to balance the many damaging plant feeders we also encounter, such as stink bugs, plant bugs, lace bugs, squash bugs, boxelder bugs, and others. The aquatic kinds will often leave their ponds and creeks and go for a flight, perhaps looking to expand their range a bit. It is not unusual to have them stop over in your backyard pool for a few days, just long enough to realize that there aren’t enough other bugs there to keep them going, and then off they go again. You can read about these guys and other swimming pool visitors in another BugInfo article on “Bugs in the Pool”.

What should you do about Assassin Bugs in and around your home? Well, those found in your gardens, as we have mentioned, may be far more beneficial to you than they are threatening, and should be enjoyed and left alone. Not all bugs on your plants need to be killed. The challenge is to learn to recognize the good ones and be able to separate them from the ones needing attention. Some excellent books can be found in the Garden and Nature sections in many bookstores, offering good pictures and information on many insects of the landscape. It generally will be undesirable, however, to have these insects inside the home, and this means maintaining the home so that you can exclude unwanted visitors. Windows and doors should be kept closed or screened, gaps large enough to admit insects around windows or doors should be permanently sealed with the appropriate material, and you should ensure you don’t carry hitch-hiking bugs in with firewood, flowers, the morning paper, or other items brought in from the outside.

Nests of wild animals should be discouraged or removed from your property, since many of the blood-feeding species commonly cohabit with rodents such as wood rats. Maintain wood piles and other materials stored outdoors by stacking it carefully off the soil and away from the sides of the structure. If you live in a part of the country where the true Kissing Bugs may also be you can minimize the concern indoors by eliminating as many open cracks or crevices as possible inside the home, particularly the bedroom. Keep your bed a foot away from walls, since the Triatoma kissing bugs prefer to walk to their meal rather than fly. Always consider contacting a licensed professional pest management company if you feel that a pesticide application may be in order. These folks will have training and equipment to allow them to do the job properly, and can offer a wide variety of choices in the products they can use.