Glossina fuscipes is a riverine fly species in the genus Glossina, which are commonly known as tsetse flies. Typically found in sub-Saharan Africa but with a small Arabian range, G. fuscipes is a regional vector of African trypanosomiasis, commonly known as sleeping sickness, that causes significant rates of morbidity and mortality among humans and livestock. Consequently, the species is among several being targeted by researchers and veterinary and public health authorities for population control as a method for controlling the disease.
Physical description G. fuscipes are often brown or grey-brown in color. Their bodies tend to have varied dark and light patches, effectively camouflaging them on surfaces such as bark, rock, or soil. At rest, G. fuscipes appear slim as they fold their wings on their backs so that one lies on top of the other. This is in contrast to houseflies and blowflies whose wings project outward at an angle while resting on their backs. Following a blood meal, the insect's abdomen will appear large, rounded and red.
Males When the male G. fuscipes is examined from the ventral side, a rounded structure named the hypopygium can be seen at the posterior end of the abdomen. Immediately in front of the hypopygium is a plate bearing dark hairs called hectors. Both the hypopygium and the hectors help distinguish male from females and serve to grasp onto the end of the female abdomen during mating. As copulation commences, the hypopygium unfolds to uncover superior and inferior claspers as well as the aedeagus.
Females The end of the female abdomen lacks any significant structures that would be the counterpart of the male hypopygium and hectors; however, females display a vulva, which can exhibit several small plates that aid in species identification.
Life cycle
Egg stage In a few hours, the sperm move from the spermatophore into the spermatheca, where they remain active for the remainder of the female's life. Eggs are fertilized immediately as they enter the uterus by sperm from the spermatheca that come into contact and penetrate the anterior portion of the egg. The fertilized egg remains in the uterus for about four days as the instar larva begins to develop. Once she has mated, a female can produce larvae for the remainder of her life. At about 25 °C, a female fly will produce mature larva every 9–10 days with the exception of the first, which may take up to 18–20 days. Lower temperatures result in a lower rate of breeding whereas higher temperatures increase the rate of breeding. Temperatures either too high or too low may cease breeding altogether.
Larva The G. fuscipes larva in passes through three instars as it grows up to when the fully grown larva is dropped by a female fly. The larva has a mouth at the anterior end and two spiracles at the posterior end. Rather unusually, the larva spends most of its time and does all its feeding within the mother's body. Apart from food stored in the egg, the food supply for the three larval instar stages comes from the mother's milk gland. The milky secretions of this gland are expelled out of the gland duct at the head end of the larva. The larva sucks up the milky secretion and passes it directly to the midgut where it is slowly digested and assimilated. For air supply, the larva depends on air entering the vulva of the female. The air must pass into the female's posterior spiracles or polypneustic lobes to reach the larva.
Abortion If a larva fails to reach its full size, it will be prematurely expelled from the uterus. The aborted larva dies. Abortions could be due to the mother fly not obtaining enough food or also when carelessly handled or exposed to insecticide. Eggs are subjected to abortion for the same reasons.
Pupa The pupa is a dark brown, shorter than the larva that produced it, and rounded with polypneustic lobes at the posterior end. The lobes are distinctively shaped and can help to distinguish the G. fuscipes pupa from that of other flies. The pupa also has a hard case on its outside called the puparium. The pupal stage lasts about four to five weeks according to temperature. Higher temperatures shorten the pupal period. In contrast, lower temperatures lengthen the pupal period to more than 50 days in certain climates. However, temperature extremes will cause death.
Adult When ready to emerge, the young adult fly expands its ptilinum to burst open puparium's end. Out of the fresh hole and surrounding soil, the adult emerges by using the ptilinum, struggling to the top of the soil and into open air. At this stage, the adult's body is very soft while its wings are small and crumpled. After a few urinations, the wings will expand towards their proper size. From the time between the emergence of the fly and its first meal, the adult is called a teneral fly. After the first blood meal has been taken, the fly is then termed a non-teneral fly.
Reproduction
Mating During mating, males settle on the back of the female. Claspers at the posterior end of the male abdomen unfold in order to grip the end of the female abdomen. This mating position may be maintained for an hour or two before the duo parts. Females typically mate a young age, either before or around the same time of their first blood meals. Females usually mate only once in their lives though it is possible mate more than once, whereas males tend to mate several times. Older males are more likely to mate successfully than very young males. During mating, the aedeagus is inserted into the vulva and reaches into the uterus as far as the spermatheca exit. A sizable ball of sperm is deposited there in the form of a spermatophore. At the conclusion of mating, the male releases his grip on the female before flying away.
Distribution and habitat G. fuscipes ranges across a vast region in Central and Eastern Africa, spanning from Cameroon and Gabon in the west to Kenya and Ethiopia in the east, and from Chad and Sudan in the north to Angola, the Democratic Republic of the Congo and Zambia in the south. A subpopulation of G. f. fuscipes exists in the very southern part of the Arabian Peninsula. G. f. f. and G. m. submorsitans are the only subspecies of Glossina which survive outside Africa, including in southwestern Saudi Arabia. They prefer high-humidity areas, namely biomes such as mangrove swamps, rain forests, lake shores, and gallery forests along rivers.
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