- Tsetse fly - Classification
- Class :
- Insecta
- Order :
- Diptera
- Family :
- Glossinidae
- Genus :
- Glossina
Definition
Tsetse flies or glossina are insects of African or New World origin. Approximately 31 species are known, divided into 3 groups based on their ecotype:
- Glossina «Palpalis» :
- live near rivers, in dense vegetation near the water,
- Glossina «Morsitans» :
- live in wooded savannahs and dense bush,
- Glossina «fusca» :
- live in forest areas.
As a blood-sucking insect, the tsetse fly is a potential disease vector. It transmits sleeping sickness.
Morphology
The tsetse fly is an insect of the order diptera. It is a long, hardy fly, blackish brown in colour. It is 6 to 16 mm long. The body is divided into 3 parts: the head, the thorax and the abdomen.
The head has mouth parts including a proboscis that it uses to bite. The thorax, made up of 3 segments, has 3 pairs of legs, 1 pair of wings and 1 pair of halteres.
Life cycle
The lifespan of tsetse flies is relatively long (with a record of nearly a year) but varies from one species to another. After mating, the first 2 larval stages take place in the uterus, then the fly deposits the larvae (between 5 and 7) in a favourable spot (sandy clay soils in shady areas). Within 2 hours, the larvae burrow into the soil transform into pupae. A 4th larval stage takes place in the puparium before producing a young tsetse that will fly after its body hardens.
The tsetse fly bites mainly during the day, particularly very early in the morning and late in the evening. During the day, it is active for 5 to 30 minutes, and spends the rest of the time ensconced in low (<3 m), shady hiding places (tree trunks, under leaves, etc.). At night, it goes up higher in the vegetation (from 2.5 m to 4 m) and rests on leaves.
Feeding habits
Both males and females feed on blood.
Bites
Tsetse flies bite to draw blood, which they need for nourishment. They take a meal equivalent to their body weight about every 2 to 4 days, and food preferences are stricter in some species than in others (humans, oxen, crocodiles, etc.).
Tsetse flies locate their prey using sensory stimuli: olfactory and visual. Initially, they are guided by odours given off by their targets: lactic acid, phenols, carbon dioxide, etc., then visual factors become more important. The more mobile the prey, the easier it is for the tsetse to locate it.
Blood is drawn using the proboscis, which is found on the head. A tsetse fly infected with trypanosoma will inject it into its target during the bite. This is how they transmit sleeping sickness.