Tsetse fly
Large biting flies that transmit trypanosomiasis in sub-Saharan Africa.
Tsetse flies, sometimes called tik-tik flies, are large, blood-feeding insects found across much of tropical Africa. They belong to the genus *Glossina*, which is the sole genus in the family Glossinidae. These flies are obligate parasites, meaning they must feed on the blood of vertebrate animals to survive. Their role as biological vectors of trypanosomes—the parasites that cause both human and animal trypanosomiasis—has made them a major focus of scientific study, with significant economic and public health impacts in sub-Saharan Africa.
You can tell tsetse flies apart from other large flies by two key features. First, when resting, they fold their wings flat over their abdomen, one directly on top of the other. Second, they have a long proboscis that points straight forward, attached to the underside of the head by a distinct bulb. Fossilized tsetse have been found in Paleogene rocks in the United States and Germany. Today, there are 23 living species of tsetse flies across Africa and the Arabian Peninsula.
In English, especially in scientific and development circles, the term "tsetse" (without "fly") has become more common. The word is derived from the Tswana (Setswana) language, where it is pronounced *tseh-tseh*, and similar sounds are used in other African languages. During World War II, a British de Havilland antisubmarine aircraft called the Tsetse Mosquito helped spread the term among native English speakers.
Entomologists have a relatively thorough understanding of tsetse biology, thanks to the flies' medical, veterinary, and economic importance, their ability to be raised in labs, and their large size, which makes them easier to study.
Tsetse flies go through three distinct forms: third-instar larvae, pupae, and adults. The larvae separate from their mother during the third instar, looking like typical maggots, but this stage lasts only a few hours and is rarely seen outside a lab. Next, they form a hard outer case called a puparium and become pupae—small, oblong, hard-shelled structures under a centimeter long, with two small dark lobes at the tail end for breathing. Inside the puparial shell, they complete their transformation. Finally, they emerge as adult flies, which are relatively large (0.5 to 1.5 centimeters long) and have a distinctive shape that makes them easy to recognize.
Quick Facts
- Taxon
- Glossina
Facts from the source article.
Lore & Background
Tsetse flies have an unusual life cycle, likely due to the richness of their blood food source. A female fertilizes only one egg at a time and retains each egg within her uterus, where the offspring develops internally during the first three larval stages in an adaptation called adenotrophic viviparity. The female feeds the developing offspring with a milky substance secreted by a modified gland. In the third larval stage, the larvae leave the uterus and crawl into the ground, developing a hard outer shell (puparial case) within which they complete their transformation into adult flies. The larval stage lasts four to ten days, and all development prior to emerging as an adult after 35 days occurs with only the nutrition provided by the mother fly.
Tsetse flies can be distinguished from other large flies by two easily observed features: they fold their wings over their abdomens completely when resting, and they have a long proboscis extending directly forward, attached by a distinct bulb to the bottom of their heads. Fossilized tsetse specimens have been recovered from Paleogene rocks in the United States and Germany. Twenty-three extant species are known from the African continent and the Arabian Peninsula. The genome of Glossina morsitans was sequenced in 2014.
Reader's Guide
Tsetse flies are of major significance due to their role as biological vectors of trypanosomes, which cause human and animal trypanosomiasis in sub-Saharan Africa. This has pronounced economic and public health consequences, affecting both human populations and livestock. Their biology is relatively well understood because of their medical, veterinary, and economic importance, as well as their ability to be raised in a laboratory and their relatively large size, which facilitates analysis. Tsetse flies have at least three bacterial symbionts: Wigglesworthia, Sodalis, and Wolbachia. The salivary gland hypertrophy virus causes abnormal bleeding in the lobes of the crop of certain subspecies. The term 'tsetse' without the 'fly' has become more common in English, particularly in scientific and development communities. During World War II, a British de Havilland antisubmarine aircraft known as the Tsetse Mosquito helped establish the term in commonplace use among native English speakers. Up to 34 species and subspecies are recognized, depending on the classification used, and all are placed in the single genus Glossina, with most considering the genus as the sole member of the family Glossinidae.
Did You Know?
- Tsetse flies fold their wings completely over their abdomens when resting, with one wing resting directly on top of the other.
- Waterbuck produce volatiles that act as repellents against Glossina.
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