The life cycle of the tsetse fly (1987): Entire title

there are 22 species of tsti flies all of which can carry trypanosomes that cause diseases in animals some are vectors of human trypanosomiasis sleeping sickness adult flies measure from 6 to 14 mm in length and are found only in tropical Africa their habitats range from rainforest to dry Savannah Woodland the tly can be distinguished from other flies by the pattern of the veins in the wing forming the so-called Hatchet cell it also has a prosis that projects forwards a widespread and economically important species glossina morsitans occurs in safana Woodlands concentrating in areas of denser vegetation at the end of the dry season when temperatures are high and humidity is low tetu flies feed exclusively on blood this one is on a man's hand the various species have different feeding preferences glossina morans often feeds on warthogs it is also attracted to antelopes such as the bush buck and it feeds on cattle while they are grazing in the bush here are two lightly colored young flies feeding the fly's tubular mouth parts are lowered and inserted into the tissues of the host in this case human the mouth Parts break up tiny capillary blood vessels Under the Skin forming a pool from which blood is sucked up into the fly the fly swells up as it feeds and the amount of blood taken up greatly exceeds the weight of the fly [Music] itself male Tes can easily be distinguished from females by the presence of the hypopygium the external genitalia at the end of the abdomen of the male and this is a female female flies mate when very young probably most do so when taking their first blood meal a nonvolatile contact sex recognition pheromone in the cuticle of the female assists in pear formation if a decoy is soaked in a ution of this substance male flies will attempt to mate with it the Flies can remain paired for several hours and although females May mate more than once only one pairing is necessary because sperms are stored in the speri of the female this diagram shows the sexual organs of a female tsti here is the vagina the uterus the ovaries the oviduct the sperm duct and the speri when mating a spermatophore a bag of sperms is deposited by the male near the ends of the spermathecal ducts sperm leave the sperm four and move into the speri unlike most insects that produce large numbers of eggs the tsif fly gives birth to one living lava at a time an egg is ovulated into the uterus from the right ovary when the fly is about 9 days old it is fertilized by a sperm from the speri and the embryo develops after about 4 days the egg hatches into a first instar lava which feeds on milk produced by the uterine glands the lava mols twice it comes to occupy most of the mother's abdomen replacing the original blood meal as it grows the pregnant fly selects a shady spot settles on soft Leaf litter soil or sand and gives birth to the fully formed lava it comes out tail first and the black objects on the rear end of the lava are respiratory organs the potic Globes the maggot weighs almost as much as its mother and from the moment of birth is very active it Burrows head first into the soil by peristaltic movements while its mother Waits when she flies away it will be to obtain another blood meal and to produce another lava in 9 days time when the lava has gone deep enough it stops moving the Laval cuticle hardens and seen here on the surface and speed it up changes in color from white to black the lava has now become the puparium and the adult develops inside it two molts take place within the puparium the first produces the pupa and the second the Imago here you can see the changes by x-ray like all stages of the life cycle the duration of the puparial period depends on the ambient temperature at a mean temperature of 25° C it lasts about 30 days this is the best stage at which to collect sety flies for laboratory work here soil from a dry riverbed is being saved and the pupy collected when this is ready to emerge the amago breaks the anterior end of the puparium the balloon-like tum on the head of the fly between its eyes expands and contracts repeatedly and helps it to get out the fly is on its back its prosi Springs out and it slowly struggles out of the puparium normally of course all this takes place Underground movements of the tum assist the upward passage of the insect through the soil the fly breaks through to the surface and rests while its wing veins fill with fluid the wings gradually expand and then dry out this takes several minutes here you see the process speed it up five times the fly has some food reserves left over from the puparial stage but it's important for it to obtain its first blood meal as soon as possible when its wings are strong enough the fly goes in search of a new host and the cycle is complete