Abortions can be caused by the mother fly not obtaining sufficient food, and may also occur when the fly is carelessly handled, or when it comes into contact with insecticide. Once mated, a female can produce larvae for the rest of her life. There are three larval instars in Glossina up to the time when the fully grown larva is dropped by the female fly: the first, second and third instars. In this way the young fly struggles to the top of the soil and out into the open air. During mating, the male penis is inserted into the vulva, reaching into the uterus as far as the exit of the spermathecal ducts. Rarely, T. b. gambiense may be acquired congenitally if the mother is infected during pregnancy. Life cycle image and information courtesy of DPDx. Tsetse are found over an estimated area of at least 10 million square kilometers on land governed by 36 different countries, which makes coordination and the institution of public health initiatives difficult. This maternal care and the deposition of individual puparia by different species in particular microhabitats present unique challenges to controlling the adults and offspring. 3.3.4 Feeding by the larva (Figure 3.1 A) Apart from the food already in the egg, all the food of the three larval instars comes from the milk gland of the mother fly. The fully grown larva has a pair of large black swellings at the posterior end. The larva sucks up this secretion and passes it straight to the midgut. As with other flies, the larva in Glossinapasses through several stages or instars, as it grows. The aborted larva dies. Medical and Veterinary Entomology (Third Edition), https://doi.org/10.1016/B978-0-12-814043-7.00018-2. The life cycle of the tsetse fly (1987) Pt. 3.3.1 First instar larva This is the stage that emerges from the egg. The body works its way out of the hole so made, and also gets through the surrounding soil by using the ptilinum. The unusual feature of the Glossina life history is that the larva spends practically all its time, and does all its feeding, within the body of the female fly (Figure 3.1 A). Females usually mate only once in their lives but some may mate more than once; males can mate several times. Copyright © 2020 Elsevier B.V. or its licensors or contributors. Tsetse females generally live for about 20–40 days but may have a maximum life span of 3–4 months. The rest of the larva is white in colour. About nine days later, the mother produces a larva which burrows into the ground where it pupates. Lower temperatures give a lower rate of breeding; higher temperatures increase the rate of breeding. The second instar lasts two days, and the larva grows to a length of 4.5 mm (G. morsitans). The pupa is slightly shorter than the larva that produces it. The males typically mate only once or twice during their lives and apparently survive in the wild for 2–3 weeks (Glasgow, 1963; Potts, 1973). The mating of tsetse flies probably takes place near to or on host animals. 3.6.1 Emergence of the adult fly (Figure 3.2 B) When ready to emerge the young adult fly expands its ptilinum (see 1.3.4) to burst open the end of the puparium. However, temperatures that are too high or too low will cause breeding to stop altogether. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. The polypneustic lobes are at first white, becoming black later. This will usually be a place where there is a patch of loose sandy soil, sheltered by an overhanging rock, branch or twig. Fig. At the end of this period, the adult fly is ready to emerge. 3.3.3 Third instar larva (Figure 3.1 B) This is also a stage of rapid growth and development. The first instar lasts for about 1 day. By continuing you agree to the use of cookies. The larva burrows into the ground and out of sight. To either side of the posterior spiracles are swellings, and between the spiracles is an area of small spines. The third instar lasts just over two days and the larva grows to a length of 6–7 mm (G. morsitans). Higher temperatures shorten the pupal period; lower temperatures lengthen the pupal period (to more than 50 days in some climates). The female flies away. Sleeping sickness is not found wherever tsetse are known to occur because several species do not readily feed on humans, but nagana is found everywhere that tsetse are distributed. Sperm remain active in the spermathecae for the rest of the female's life. The ptilinum cannot easily be everted. The larva has a mouth at the anterior end, and two posterior spiracles. Most of the weight and volume of the third instar larva is due to the gut which contains large amounts of unassimilated food. At this stage the body is very soft and the wings are small and crumpled. 3.3.6 Abortion Sometimes a larva fails to reach its full size and is expelled from the uterus before the usual time. The larva then works itself backward cut of the vulva of the female, helped by pushing movements of the female's legs, and drops to the ground.
Calvin And Hobbes Comics Pdf, How To Make Shahi Paneer, Giant Sequoia Bonsai Forest, Spacebar Counter 1 Minute, Queen Elizabeth Academy Atherstone Uniform, Alavi Beeja Benefits In Kannada, Ghost Pepper Potato Chips Calories, 12" Explore Scientific, True Basic Tees, Basic Physics Test, Nestlé Hr Department Contact Number, Sea Otter Energy,