During mating, the male penis is inserted into the vulva, reaching into the uterus as far as the exit of the spermathecal ducts. The life cycle of the tsetse fly (1987) Pt. 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 males typically mate only once or twice during their lives and apparently survive in the wild for 2–3 weeks (Glasgow, 1963; Potts, 1973). In the next few hours sperm make their way up from the spermatophore into the spermathecal ducts and the spermathecae. Fig. The cycle in the fly takes approximately 3 weeks. The aborted larva dies. Fig. Copyright © 2020 Elsevier B.V. or its licensors or contributors. Medical and Veterinary Entomology (Third Edition), https://doi.org/10.1016/B978-0-12-814043-7.00018-2. However, temperatures that are too high or too low will cause breeding to stop altogether. 3.3.2 Second instar larva This is a stage of rapid growth and development. Copyright © 2019 Elsevier Inc. All rights reserved. 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. It breaks out of the chorion (see using a sharp egg tooth. The milky secretion of this gland is poured out of the duct of the gland, at the head end of the larva. 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). To either side of the posterior spiracles are swellings, and between the spiracles is an area of small spines. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. four days, while development of the first instar larva takes place inside. Within an hour or two the larva becomes barrel-shaped, darkens and may then be called a pupa. The rest of the larva is white in colour. The fully grown larva has a pair of large black swellings at the posterior end. The first instar grows to 1.8 mm (G.morsitans)before changing to the next stage by getting rid of its old skin. At the end of this period, the adult fly is ready to emerge. 2 of 2 - YouTube After a few urinates the wings begin to expand to reach their proper size. About nine days later, the mother produces a larva which burrows into the ground where it pupates. Sleeping sickness has hampered human productivity, and nagana has prevented the widespread use of domestic animals as sources of food, transport, labor, or fertilizer. 3.3.3 Third instar larva (Figure 3.1 B) This is also a stage of rapid growth and development. This is called an abortion. LIFE CYCLE 3.1 MATINS. At this stage the body is very soft and the wings are small and crumpled. Tsetse females generally live for about 20–40 days but may have a maximum life span of 3–4 months. A large ball of sperm is deposited there in a spermatophore. The larva burrows into the ground and out of sight. 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. Most of the weight and volume of the third instar larva is due to the gut which contains large amounts of unassimilated food. 3.3.6 Abortion Sometimes a larva fails to reach its full size and is expelled from the uterus before the usual time. 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. At the end of mating, the male releases his grip on the female and flies away. 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. When the larva in the uterus is fully grown, the female Glossina flies around looking for a suitable area in which to drop it. 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. Tsetse flies are obligately hematophagous and are in a group of flies with the unusual characteristic of having the female retain the larval offspring until it is fully grown and just about ready to pupate.


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