Tsetse Fly

Quick Take

• This fly's bite is so stealthy you may never feel it. How does it pull that off?
• Its reproduction is bizarre: one mating, and she's pregnant for life.
• One color lures these flies to their doom, but there's a catch that makes it hard to use.
• Scientists found something in its mouth that no other insect has.

Tsetse flies are a type of blood-sucking insect that lives in diverse locations in Sub-Saharan Africa. There are about 31 different species and subspecies of tsetse flies. The pronunciation of tsetse is tse-see, according to Merriam-Webster. This insect’s deadly bite, which you may not even notice, kills thousands each year.

5 Incredible Tsetse Fly Facts

• Both male and female Tsetse flies draw blood from humans by biting them.
• The female tsetse fly stays pregnant for her entire lifespan, which is about 4 months. The male only impregnates her once, and she holds the eggs in a special sack where she develops them one at a time.
• Diseases transmitted by the tsetse fly now cause fewer than 1,000 reported human cases annually.
• Tsetse babies develop inside the mother fly before being buried in the ground inside a small, hard-shelled puparium before they finally metamorphose into a fly.
• Tsetse flies are also called tik-tik flies.

Species, Types, and Scientific Name

Tsetse flies are African blood-feeding dipterans in the genus Glossina. The pronunciation of Glossina is glos·​si·​na, according to Merriam-Webster. Speciation of Tsetse varies around the world. These flies are insects that belong to the Diptera order. They are all part of the Hippoboscoidea superfamily and the Glossinidae family.

Biologists divide the Glossina genus into three subgenera based on their behavior, how their molecules are arranged, and their morphological structure. It is often easier to think about them being divided into groups by their preferred location because different types live in different habitats.

• Glossina (the morsitans group): Generally live in savannah areas of Africa.
• Austenina (the fusca group): Found in the forest.
• Nemorhina (the palpalis group): Includes seven species often called ‘riverine’ and ‘lacustrine’ flies.

Appearance: How to Identify Tsetse Flies

Tsetse flies are between 0.25 and 0.5 inches big, or about the size of a housefly. Depending on the species, they are yellowish-brown to dark brown. All tsetse flies have a gray area on their thorax. You may see faint bands on their abdomens.

The head of a tik-tik fly has large eyes on each side of its head. The thorax is made up of three fused segments and is large for the size of the fly. The abdomen is short and wide. It gets noticeably wider when the fly eats.

Tsetse flies can look different depending on the phase of the life cycle that they are in currently. The life cycle begins with the egg hatching. Then, about four days later, the male has sex with the female. While the act only happens once, the female remains pregnant for the rest of her life. An egg is passed into a special sack on her body every nine days, where she feeds it a unique substance. In a couple of days, she lays the egg, and the life cycle begins again. Females will continue to lay eggs throughout their life cycle, which lasts for about 4 months.

Entomologists look for at least four characteristics when deciding if an insect they are examining is a member of the Glossina genus.

• Proboscis: This long, thin structure is attached to the bottom of the head and points forward.
• Wings: The tik-tik fly can fold one of its wings completely over its body and put the other one on top of the first one when it is resting.
• Hatchet cell: The middle cell of each wing looks like a hatchet.
• Bristled antennae: The tsetse fly has branched bristles that are covered in hair.

It is the bite of the tsetse fly that makes them so dangerous to humans. Researchers at the University of Bristol have discovered that the fly uses its teeth to tear through the skin and capillaries. Then, it uses its rasps to make the hole bigger. Researchers were surprised to learn that the tsetse fly projects a substance from its proboscis, a long tube in the insect’s mouth, that keeps its victim’s blood from clotting. Researchers have not found this proboscis tube in any other insect.

Habitat: Where to Find Tsetse Flies

These insects live in sub-Saharan Africa. Depending on the species, they can be found in several habitats. Most prefer to live in wooded areas. They will stay in the woods’ underbrush, where they often hide under logs or rocks. Tik-tik flies prefer to live close to their food source, as they spend most of their time resting.

Diet: What Do Tsetse Flies Eat?

These insects feed on blood. Each species has a food source that it prefers. Only one species is a generalist that feeds on any blood available, but others may feed off other sources if their preferred source is unavailable. Many species prefer to dine on animals, like cattle, and not on humans.

While it was thought that tsetse flies only fed on blood for a long time, researchers know that is not always the case. If the fly gets hungry enough and no blood is available, it may feed on water or water with sugar. This finding may be important in helping to control the tsetse fly.

Prevention: How to Get Rid of Tsetse Flies

Researchers continue to study how to get rid of tsetse flies because they are so dangerous. Some sprays can effectively control tsetse flies, but they can be costly and difficult to obtain in the needed areas.

These insects can also be trapped. They want a place to rest under a large object, and they want a source of blood. Therefore, researchers have discovered that they can trap them by providing these two things. They have also found that they are drawn to the color blue. Since these flies can see approximately 165 feet, it can be challenging to provide enough traps to cover the whole area where tsetse flies live.

Screens can also kill these insects, but they only work when the screen is covered with a repellent. The most effective screens are placed near where tsetse flies live. They are made of blue material with a black strip down the middle covered with repellent. The blue color attracts the tsetse. Then, they try to land on the black strip to rest, and they die. Keep in mind that incomes in the areas where tsetse flies live can be meager, so repellent can be very expensive.