3.6.3 Non-teneral fly (see 7.5) After the first blood meal has been taken, the underside of the abdomen appears more creamy yellow, and when held up to the light the dark shape of the last meal can be seen. Usually 12 to 15 days elapse before flies that have picked up the parasites become infective toward humans. There is no feeding by the larva after it is dropped by the female. Copyright © 2020 Elsevier B.V. or its licensors or contributors. Once mated, a female can produce larvae for the rest of her life. In the next few hours sperm make their way up from the spermatophore into the spermathecal ducts and the spermathecae. It breaks out of the chorion (see 2.5.2.2) using a sharp egg tooth. After 7 - 9 days she produces a single egg which develops into a larva within her uterus. Male tsetse fly adults may live two to three weeks, while females can live for one to four months. Here it is slowly digested and assimilated. The thorax feels firmer and harder, because of the greater development of muscles in it. 3.2 Pupal stage and emergence; A, pupa; B, young fly emerging from the pupa, with ptilinum inflated in front of head. When the larva in the uterus is fully grown, the female Glossina flies around looking for a suitable area in which to drop it. As with other flies, the larva in Glossinapasses through several stages or instars, as it grows. This maternal care and the deposition of individual puparia by different species in particular microhabitats present unique challenges to controlling the adults and offspring. Rarely, T. b. gambiense may be acquired congenitally if the mother is infected during pregnancy. However, temperatures that are too high or too low will cause breeding to stop altogether. The vast majority of human cases result from the transfer of T. brucei trypanosomes by tsetse flies as they suck human blood. The underside of the abdomen appears whitish and semi-transparent, the ptilinum can sometimes be everted when the sides of the head are squeezed between the fingers, and the body has a soft feel to it. Inside the pupa two main processes take place: the food still remaining in the midgut is digested and assimilated. This position may be held for an hour or two, before the male and female flies part company. Tsetse flies are larviparous—the larva hatches from an egg within the female—and the young develop singly within the female’s uterus, feeding on a nutrient fluid secreted by paired milk glands on her uterine wall. The egg is fertilized immediately it enters the uterus by sperm from the spermathecae coming into contact with and penetrating the anterior part of the egg. Medical and Veterinary Entomology (Third Edition), https://doi.org/10.1016/B978-0-12-814043-7.00018-2. The pupal stage usually lasts about four to five weeks, according to temperature. The epimastigotes reach the fly’s salivary glands and continue multiplication by binary fission . Copyright © 2019 Elsevier Inc. All rights reserved. Tsetse females generally live for about 20–40 days but may have a maximum life span of 3–4 months. The female tsetse settles down either on the ground or on the overhanging object. The life cycle of the tsetse fly (1987) Pt. 3.1 Side view of larva of Glossina, A, in the uterus; B, mature larva after being dropped by the female. Male flies settle on the back of the female, and the claspers at the posterior end of the male abdomen grip the end of the female abdomen. The mother continues to produce a single … The hard case on the outside of the pupa is called the puparium. The milky secretion of this gland is poured out of the duct of the gland, at the head end of the larva. They have been extensively studied because of their medical, veterinary, and economic importances, because the flies can be raised in a laboratory, and because they are relatively large, facilitating their analysis. For centuries, tsetse have been one of the greatest factors affecting the course of economic and social development in Africa. The female flies away. Too high or too low a temperature will cause the death of the pupa. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. This will usually be a place where there is a patch of loose sandy soil, sheltered by an overhanging rock, branch or twig. We use cookies to help provide and enhance our service and tailor content and ads. Life cycle image and information courtesy of DPDx. The fertilized egg remains lying in the uterus for about 3.3.6 Abortion Sometimes a larva fails to reach its full size and is expelled from the uterus before the usual time. Most of the weight and volume of the third instar larva is due to the gut which contains large amounts of unassimilated food. Fig. About nine days later, the mother produces a larva which burrows into the ground where it pupates. Sperm remain active in the spermathecae for the rest of the female's life. The fully grown larva has a pair of large black swellings at the posterior end. The pupa is a dark brown rounded object; at the posterior end are the polypneustic lobes the shape of which helps to distinguish the tsetse pupa from the pupae of other flies. At the end of this period, the adult fly is ready to emerge. This is called an abortion. At the end of mating, the male releases his grip on the female and flies away. These are the polypneustic lobes, which carry many small holes through which the larva breathes. 3.3.3 Third instar larva (Figure 3.1 B) This is also a stage of rapid growth and development. To either side of the posterior spiracles are swellings, and between the spiracles is an area of small spines. 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. Higher temperatures shorten the pupal period; lower temperatures lengthen the pupal period (to more than 50 days in some climates). The rest of the larva is white in colour. A large ball of sperm is deposited there in a spermatophore. The cycle in the fly takes approximately 3 weeks. Within an hour or two the larva becomes barrel-shaped, darkens and may then be called a pupa. The first instar grows to 1.8 mm (G.morsitans)before changing to the next stage by getting rid of its old skin. The egg may also be aborted for the same reasons. 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. Lower temperatures give a lower rate of breeding; higher temperatures increase the rate of breeding. After a few urinates the wings begin to expand to reach their proper size. Sleeping sickness has hampered human productivity, and nagana has prevented the widespread use of domestic animals as sources of food, transport, labor, or fertilizer. The larva sucks up this secretion and passes it straight to the midgut. At a temperature of about 25°C a female fly will produce a mature larva every 9–10 days, except for the first one which may take 18–20 days from the time of emergence of the fly from the puparium (see 8.5.2 and Figure 8.6). The mating of tsetse flies probably takes place near to or on host animals. The polypneustic lobes are at first white, becoming black later. The ptilinum cannot easily be everted. 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). At this stage the body is very soft and the wings are small and crumpled. Older males are better able to mate successfully than very young ones. By continuing you agree to the use of cookies. 2 of 2 - YouTube 3.3.5 Breathing by the larva For its air supply the larva depends on air entering the vulva of the female and then passing into its posterior spiracles or polypneustic lobes. The larva burrows into the ground and out of sight. The first instar lasts for about 1 day. All of the 31 known species and subspecies are capable of transmitting the trypanosome parasites that cause human sleeping sickness and disease in domestic animals that is known as nagana. The pupa is slightly shorter than the larva that produces it. Tsetse flies, with one exception, are all found in Africa. Females are mated young, before or at about the time of taking the first blood meal. Male flies settle on the back of the female, and the claspers at the posterior end of the male abdomen grip the end of the female abdomen. The third instar lasts just over two days and the larva grows to a length of 6–7 mm (G. morsitans). The second instar lasts two days, and the larva grows to a length of 4.5 mm (G. morsitans). The aborted larva dies. 3.6.2 Teneral fly (see 7.5) From the time the fly emerges to the taking of its first meal, the young fly is called a teneral fly.