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CHAPTER 2
ECOLOGY OF MORSITANS GROUP SPECIES

2.1 ECOLOGY OF GLOSSINA MORSITANS

2.1.1 Environment

2.1.1.1 Climate Glossina morsitans occurs in regions of tropical Africa having a mean annual temperature of from 19–28°C, and where it is neither very humid nor very dry.

The species is divided into three subspecies:

  1. Glossina morsitans submorsitans This is distributed as a broken belt across Africa from Gambia and Senegal, extending eastwards as far as Ethiopia and Uganda. It lives best at 24–26OC.

  2. Glossina morsitans morsitans This is widely distributed in East Africa as far south as Mozambique, and as far north as northern Tanzania. It lives best at 21.5–24OC.

  3. Glossina morsitans centralis This is distributed in Central Africa, covering parts of Botswana, Angola, Zaire, Zambia, Rwanda, Burundi, Uganda and Tanzania. Since it is separated from G.m. morsitans by a relatively narrow watershed, it probably needs the same climatic conditions as that subspecies.

At the edges of its distribution, the fly population concentrates into the cooler and moister parts of its habitat to escape the worst effects of the hot season. In these areas therefore it can behave as a riverine fly in the hot dry season.

2.1.1.2 Vegetation

  1. Typical habitats.

    The typical habitat of G. morsitans is open woodland and woodland savanna with plenty of game animals living in the area.

    In West Africa G. morsitans lives in 'doka' woodland, in which the main (dominant) tree is Isoberlinia doka (or its close relatives).

    In East and Central Africa the same kind of woodland is miombo, dominated by trees such as Isoberlinia, Brachystegia and Julbernardia.

    In addition, the species occupies dry thorn bush of Uganda and Ethiopia, for instance.

    More northerly parts of West Africa, in the Sudan vegetation zone, also contain G. morsitans. Here the dominant trees are Anogeissus, Balanites, Lannea, Combretum and certain Acacia species.

    In more southerly parts of East and Central Africa, the Zambezi-Luangwa river valleys are dominated by mopane, Colophospermum mopane; here G. morsitans can live in large numbers, and yet be absent from the hills next to the valleys.

    In West Africa, the zone to the south of doka woodlands is the southern Guinea and derived savanna. It contains G. morsitans, and the vegetation is dominated by Daniella, Hymenocardia, Detarium, Afzelia, Lophira, and Terminalia trees. There is not very much south of the equator to correspond with this vegetation zone.

  2. Other habitats.

    Glossina morsitans can change its visual behaviour and live off domestic animals, especially cattle, in the absence of game animals. This has occurred in Sudan (Koalib Hills pocket, now exterminated, where practically the only game is baboons, monkeys and hyrax); and in Nigeria the species used to live along a busy cattle trekking route passing through a densely populated and heavily cultivated area, well outside its usual range.

    The same dependence on cattle may be developing in other areas where game is absent, but where there are plenty of cattle with some trypanosomiasis.

  3. Vegetation areas not used by G. morsitans

    -   ‘Gusu’ woodland (dominated by Baikiaea trees) in parts of Botswana, Zambia and Zimbabwe. The dry sandy soil and cold winter months may kill off any pupae placed in this area.

    -   Unbroken thicket in which the canopies of trees and bushes touch and give so much shade that there is no grass growth (but small thickets may be lived in, and some pupae deposited there).

    -   Very high rainfall areas such as rain forest and mangroves.

2.1.1.3 Effect of other animal life on G. morsitans

  1. Host animals (see also Volume I, Chapter 6).

    Glossina morsitans gets from one-third to nearly a half of its food from warthog.

    Bovids are very important also, especially kudu, buffalo, bushbuck and eland. Other species may be important locally.

    The fly feeds on cattle when available, and this is the reason for its great economic importance as a vector of trypanosomiasis.

    Some animals are hardly ever used as hosts, for example zebra, impala, gazelles and wildebeest (see Volume I, 6.1.2).

  2. Predators and parasites.

    Glossina morsitans is eaten by many predator species, from small mammals and birds to other insects. Both puparia and adults are taken.

    The morsitans group is attacked by more parasites than are the other tsetse groups. Glossina morsitans has more than 30 recorded insect parasites. Those of Mutillidae (Hymenoptera) and Bombuliidae (Diptera) are probably the most important.

    Another parasite, Syntomosphyrum (Eulophidae, Hymenoptera) has been bred in large numbers for field release, in an attempt at biological control, but without any lasting success.

2.1.1.4 Effect of human activity When natural habitats are affected by man there is often a reduction in the wildlife. Glossina morsitans does not easily change its habits to feed on man and his domestic animals, and is generally one of the first species to disappear when the human population in an area grows.

Peri-domestic habits as seen in some palpalis group species are not often found (but see 2.1.1.2 (b)).

2.1.2 Behaviour of Glossina morsitans

2.1.2.1 Flight Most of the information in 1.2.1 cones from the study of G. morsitans.

2.1.2.2 Resting sites As with other species, the fly rests at higher levels in the vegetation

  1. when the weather is cooler
  2. when the air is more humid
  3. in the evening.

Towards mid-day, as the temperature rises and the humidity falls, flies move to large shaded tree trunks and rest up to about 3 m from the ground.

In the late afternoon, as the temperature falls and the humidity rises, flies move to the underside of horizontal (or nearly horizontal) branches up to 30 cm thick and from 1–6 m above the ground.

At night flies rest on the upper surface of leaves up to 9 m from ground level.

Females rest at slightly higher levels than males, and hide themselves more carefully in the cracks of tree bark, and in similar places. They are therefore more difficult to find than males.

Tsetse behaviour may vary from place to place, so that special studies have to be made on resting places for each area.

  1. During the day. Newly emerged flies perched on the underside of small branches, 2 to 4 m above the ground (Tanzania).

    In the dry season (Zambia) flies were not found above 3.6 m, with most flies concentrated on the lower part of tree trunks; bushes and fallen logs were also most used. In the rainy season (Zambia) tree trunks and grassy undergrowth were used more than branches or canopies.

    In Sudan savanna (Nigeria) flies used only the trunks of large trees, and settled up to 1.5 m above ground.

    In Northern Guinea savanna (Nigeria) flies rested on the underside of branches up to 5 m above ground. As temperature increased, more flies rested on trunks, and the height above ground decreased (to about 1 m at 38OC).

  2. At night. Most flies rested on leaves up to 6 m or more, in teak woodland (Zambia).

    Flies moved rapidly at the approach of dusk, to settle on the upper foliage (Nigeria), or twigs, leaves and small creepers at 0.3–4.6 m (Nigeria).

2.1.2.3 Response to host animals Much of the information in 1.2.3 comes from the study of G. morsitans.

2.1.2.4 Daily activity The normal daily behaviour pattern shows greatest activity just after dawn, and another period of high activity in the late afternoon.

This pattern is altered by climatic conditions.

When the average temperature is low, general activity is low. In the cool season the morning activity is reduced, and most activity is in the afternoon when the area has become warmed up.

When the average temperature is high, general activity is high. But during the times of day when the temperature is very high, then activity is greatly reduced because it becomes too high for. the tsetse to survive without shelter. Therefore in the hot season the afternoon activity is reduced.

Flies move away from regions of very bright light and will not feed in bright light. At very high temperature flies start to move towards dark places (which are cooler).

Flies are not active just after they have fed. Daily activity increases each day after feeding.

2.1.3 Populations

2.1.3.1 Pupal populations and breeding sites It is difficult to find many pupae, in comparison with the flies that can be caught.

In some areas practically all the pupae found will give rise to adult flies successfully. In other places as many as half of the pupae collected will be dead.

Rates of parasitism have been mentioned under 1.1.4.

The site chosen by the female for depositing the larva varies from season to season.

In the wet season pupae can be found under logs in open woodland.

In the hot dry season pupae can be found in patches of forest or under banks along river beds. Here, areas of loose soil with shady perching places above are often chosen. Beneath logs and in the soil shaded by leaning trees are favourite pupal sites of G. morsitans.

But there must be many other pupae sites that are more difficult to find.

2.1.3.2 Adult populations

  1. Sex ratio. Fly round catch few teneral flies and few females. But with catches using bait oxen, the proportion of females is higher.

    The proportion of females caught from resting sites may be slightly lower than the proportion of females in the area as a whole, because they select more sheltered places and slightly higher places as resting sites, than males.

  2. Age. Male G. morsitans live on average about 30 days, and females for about twice as long. Both these figures are very variable. Many flies live for much' longer.

    Techniques for estimating age are described in Volume I, Chapter 8.

  3. Physiological state. The female is nearly always mated before or while she takes her first meal. It is rare to find a female that has fed but has not mated.

    Flies landing on man in the 'head up' position are generally hungry flies.

    Flies landing on man rather than on a bait ox nearby, are hungrier than those on the bait ox.

    Fully engorged flies are often found rather low down on the resting sites. They are very inactive.

    The time from one blood meal to the next is called the feeding cycle or hunger cycle (see Volume I, 7.6). For G. morsitans this lasts about 2–3 days in the dry season and about 3–5 days during the rains.

  4. Density and dispersal. Glossina morsitans populations vary around an average level which is surprisingly steady. Seasonal variation is most obvious near the edges of the species' distribution rather than in the middle of fly belts.

    Near the hot limits of the distribution of G. morsitans (e.g. in the Sudan vegetation zone of West Africa) the greatest fly round catches are made at the end of the rains. This is also true of East Africa. Near the cold limits (in southern Africa) they are made during or at the end of the dry season.

    Estimates of population density give results varying from 40 (or less) to 400 (or more) males per square kilometer. There are more females than males, but they are more difficult to catch and therefore more difficult to count.

    During each year there are movements of G. morsitans populations according to season, especially in West Africa at the edge of the species' distribution. In West Africa the dry season habitats are within the thicker vegetation along water courses, and in the wet season flies spread out into the surrounding savanna woodland.

    Within the main areas of distribution away from the edges, G. morsitans spends more time in savanna woodlands which may be all-season habitats, especially if there are patches of thicker vegetation present. In the dry season of southern central Africa, dambo edges are fly concentration areas.

    In the southern Guinea zone of West Africa G. morsitans in the dry season concentrates around the headwaters of streams, between the thick fringing forests and the surrounding savanna woodlands.

    Certain areas are well known as places in which tsetse and trypanosomiasis are always present. These are known as 'persistent foci' (singular, focus).

    Other places may show a spread (advance) of fly, or its retreat (recession).There may be several possible causes of such advances or recessions:

    -   if cultivated land is abandoned, fly may be able to move in as the bushes and trees grow up

    -   if wild hosts increase in numbers because of protection from hunting or because of recovery from animal diseases, then more flies will be able to live in the area. The introduction of herds of domestic cattle might have the same effect

    -   if the climate is favourable for a number of years this will encourage the fly to spread and perhaps to reach areas (e.g. other river systems) where it can live permanently even after the return of less suitable climatic conditions.

    Fly recessions may be caused by the reverse of these changes. Advances and recessions may occur without any very obvious cause; they are sometimes called 'spontaneous advances' and 'spontaneous recessions'.

    Some flies, especially males, may be carried for several kilometers by animals or man (and traffic). But the proportion of flies that get carried in this way is very small.

2.1.4 Epidemiology and control Glossina morsitans is the most important vector of cattle trypanosomiasis. It is also an important vector of Trypanosoma rhodesiense, causing sleeping sickness in East and Central Africa.

It is easily infected with trypanosomes and shows high levels of infection. Average rates (all infections) are around 12%, but locally this might rise to as much as 90% (along trade cattle routes).

Fly infections with T. vivax are commoner than those with T. congolense, and these are commoner than those with T. brucei (see Volume I, 6.5.1).

Warthog (and other pigs) do not support T. vivax, so that where G. morsitans does most of its feeding on these animals, the proportion of T. vivax infections in the fly is low, and may be less than the T. congolense infection rate.

Drug treatment of cattle leading to the quick suppression of T. vivax can lead to the same situation.

A method of G. morsitans control that was widely used in the past was discriminative clearing (see Volume III, Chapter 2). Sometimes it worked and sometimes it did not. It was based on the idea that removal of woody vegetation from certain limited areas (concentration areas) would destroy the fly population. It is now believed that in at least some parts of the distribution of G. morsitans, the fly population is much more evenly distributed in the different vegetation . types, than has been thought in the past. In other words, the concentration area need not be the only place that the tsetse lives in. This could explain the failures of some discriminative clearing exercises in the past.

2.2 ECOLOGY OF GLOSSINA SWYNNERTONI

2.2.1 Environment Glossina swynnertoni is distributed in belts in northern Tanzania, and across the border in Kenya. It does not extend further probably because of competition from G. morsitans,which it closely resembles. However, when G. morsitans was released into G. swynnertoni areas, both species were able to live because G. morsitans took up a slightly different part of the habitat.

The environment of the area is dry. There are thickets and large areas of mbuga, with Acacia. The miombo of the area is not inhabited by G. swynnertoni.

2.2.2 Resting sites By day in the wet season G. swynnertoni rests on the underside of branches of small trees, 1–4.5 m above the ground.

Sliqhly more than half of the flies rest on branches 2.5–10 cm in diameter 1.25–3.75 m above the ground.

As night comes, the flies move to rest on the upper surface of leaves, mainly 0.5–3 m above the ground.

2.2.3 Host animals Like G. morsitans, G. swynnertoni relies heavily upon the warthog for its blood meals. Between 60–70% of the food of the species cones from this host animal. Other important host animals are giraffe and buffalo.

2.2.4 Predators and parasites Ants (Pheidole sp) are thought to be the roost important predators of pupae, and they have been seen carrying off tsetse pupae.

Predators were more effective in destroying pupae in unburnt bush than in burnt bush. The reason is not certain.

Spiders (Hersilia setifrons) were seen to catch many G. swynnertoni adults, on tree trunks. In one area up to 17% of the tsetse population were caught each week by spiders.

Thyridanthrax has been recorded as parasitising G. swynnertoni pupae.

2.2.5 Behaviour Male flies are more often caught by men on fly rounds during the second and third week of life. This probably indicates that teneral males are rather inactive compared with other males.

Man is not favoured as a host animal, but flies do form following swarms behind him.

The feeding cycle (interval between feeds) of G. swynnertoni is 4–5 days in the dry season.

The method of judging the hunger state of adult males can be used on G. swynnertoni (see Volume I, Chapter 7).

Oxen moving 140 m (450 ft.) away can be seen by G. swynnertoni in a good light, but at 180 m (600 ft.) they cannot. A calf hidden behind a screen attracts more flies than a screen by itself.

2.2.6 Breeding sites Pupae are found especially in open thickets. The spot chosen for depositing a larva is often immediately below a horizontal branch. Holes in trees are also used, for example in baobab.

Breeding goes on throughout the year (tenerals can always be found) but wet season breeding sites are difficult to discover.

2.2.7 Insemination rates Non-teneral females are nearly always inseminated (mated).

2.2.8 Age of population The wing fray method of estimating the age of male flies can be used on G. swynnertoni.

One study showed that the average life of a male lasted between 2 and 4 1/2 weeks.

2.2.9 Seasonal movements Like G. morsitans, G. swynnertoni increases its range in the wet season, and becomes more concentrated in smaller areas in the dry season. For example, open mbuga with stands of Acacia drepanolobium forms a temporary dry season habitat for G. swynnertoni, but thorn bush on slightly higher ground acts as the permanent breeding area. Locally, a very thin tree cover may allow tsetse breeding, if the air is humid (as it is, close to Lake Victoria) and if game animals are abundant.

2.2.10 Epidemiology and control From 1922 to 1935 there was a local outbreak of Rhodesian sleeping sick ness in Tanzania, in which G. swynnertoni was the vector. The fly is also an effective vector of cattle trypanosomiasis.

Areas of G. swynnertoni have been cleared, experimentally, by the destruction of game animals, but this is not a method in use at present.

Insecticide spray has been applied to resting places of G. swynnertoni in open bushland in Tanzania, concentrating on the underside of brandies 1.2–2.8 m above the ground, the branches being 2.5–10 cm in diameter and sloping at less than 35° from the horizontal.

2.3 ECOLOGY OF GLOSSINA LONGIPALPIS

2.3.1 The environment Glossina longipalpis extends from Senegal in the west to north-west Zaire in the east. There are large gaps in the distribution of the species, especially between east Nigeria and north-west Zaire.

It inhabits savanna woodland immediately north of the blocks of rain forest. Its north-south distribution is very limited. Near its northern limit it overlaps in some areas with the southern limit of G. morsitans submorsitans.

It does not occur in rain forest or in dry open woodland savanna. Vegetation between these two types seems to be more suitable. Such vegetation has been called forest-savanna mosaic, forest-island vegetation or derived savanna. Much of this vegetation has grown up following shifting agriculture by man.

Further north it also occurs in moist savanna (southern Guinea savanna) mainly in riverine gallery forest vegetation. The same areas are often also inhabited by G. palpalis.

During the dry season it concentrates in gallery forests and forest islands but seasonal movements are less than those made by G. morsitans.

2.3.2 Behaviour Glossina longipalpis feeds mostly on species of Bovidae, especially the bushbuck, if these hosts are available. It will also feed on wild pigs (Suidae).

Flies are most active at temperatures of about 25°C and at relative humidities of about 85%.

Little is known about the resting sites of G. longipalpis. Male flies particularly are attracted to the vicinity of man, although they do not often land on him. They are often seen resting on twigs, leaves and blades of grass, especially in dappled sunlight in clearings. They fly rapidly front one site to another.

2.3.3 Populations Puparia of G. longipalpis have been found under logs in forest islands during the dry season and early rains. The wet season breeding sites are unknown.

When man is the bait, most flies are caught from nearby twigs, leaves and blades of grass. Most (often about 98%) of these flies are males from the following swarm.

The percentage of females in the catch from man increases in the early morning and late evening. It is also higher at the end of the dry season.

With an ox as bait many more flies are caught. The female percentage is then 40–50%.

More hungry flies are caught when an ox is the bait. This is probably because ox is an attractive host for feeding purposes, whereas male flies are mainly attracted to man simply as a moving object, to which females may also be attracted, rather than to feed.

Numbers of flies caught decline throughout the dry season and are lowest in the early rains. Numbers rapidly increase during the wet season and are highest early in the dry season.

Populations of G. longipalpis are generally heavily infected with trypanosomes. The infection rate in a large sample of* flies from southern Nigeria was 21.5%.

Glossina longipalpis could become important as a vector of animal trypanosomiasis if cattle were to come within range, and the fly does prevent the keeping of cattle in some good grazing areas. No attempts have been made to control this species, although plans to do so have been made in the past, for instance in Ghana.

2.4 ECOLOGY OF GLOSSINA PALLIDIPES

2.4.1 Environment Glossina pallidipes is patchily distributed throughout eastern Africa, from Ethiopia, Sudan and Somalia in the north, to Zimbabwe and Mozambique to the south. Parts of eastern Zaire and Zambia are also infested. The species used to live in parts of South Africa, but it has been eradicated from there.

Glossina pallidipes requires thickets and does not occur above 2000 m (6000 ft.). Under mild climatic conditions this species can spread through areas of scattered thickets, woodland and even open country. Rarest edges along the Kenya coast are infested with G. pallidipes.

Untrimmed hedges and tree crops can encourage G. pallidipes infestation.

Like its close relative G. longipalpis, G. pallidipes depends cm bushbuck for most of its food.

2.4.2 Resting sites Day time: at temperatures between 20o and 30O (Zimbabwe) flies rest on the under side of horizontal or nearly horizontal branches, up to 12 m above ground. At higher temperatures, flies move to lower cooler resting sites, such as tree trunks near ground level, the underside of fallen logs, the cracks in bark, and rot holes in trees.

Night time: flies move to rest on leaves

2.5 m to 4 m above the ground.

2.4.3 Host animals This species depends very heavily on bushbuck for its food. Warthog, bushpig and buffalo are also important. Roan antelope is readily fed upon when available.

In particular areas, other hosts may replace buchbuck as the main source of food. For example, in Masai Mara (Kenya) buffalo is the main host.

For one G. pallidipes population, it was estimated that on average each host animal (usually bushpig or bushbuck) supported 1163 tsetses, and gave 291 blood meals each day.

2.4.4 Parasites Mutillids, Thyridanthrax (Bombyliidae) and various parasitic wasps have been reported as parasites of G. pallidipes.

In Kiboko (Kenya) and Mwalewa (Kenya) a high rate of parasitism by Thyridanthrax was found.

2.4.5 Behaviour Daily activity of G. pallidipes, as measured by the netting of flies coming to bait cattle at Lugala (Uganda) was different in the two sexes. Male catches increased throughout the day (whatever the season) until just before sunset, when the catch quickly dropped to zero. Female catches rose to reach a moderate level at about midday, which continued until sunset, when the catch dropped.

But in some places in Kenya the catch showed a morning maximum and another smaller afternoon maximum, the two being separated by a rather inactive midday period.

The reasons for these differences are not understood.

In Zimbabwe in the hot dry season, there was a slight morning peak in feeding activity, but feeding was greatest in the afternoon, stopping suddenly at 18.45–19.00 hours. In the rains there was no morning maximum.

There may be some activity and feeding at night.

2.4.6 Breeding sites Along the Lambwe Valley (Kenya) breeding sites were found mostly along the well-drained sheltered banks of the river courses with Sansevieria as the ground layer vegetation. At Kilifi (Kenya) pupae were found scattered at random over the thicket and forest floor. At Mwalewa and Nkruman (Kenya) pupae were found mainly under shrubs giving the darkest shade, especially where there low overhanging branches.

In Zimbabwe, G. pallidipes uses sandy river beds in the cool dry season, and animal burrows in the hot dry season. Some pupae have been found under fallen logs in the wet season, but few pupae are found.

2.4.7 Adult populations Very few teneral females are inseminated, so it is believed that mating takes place after the first blood meal has been taken by the female.

In a sample of flies collected from bait oxen, the flies taken during the middle hours of the day were older than the flies taken in the early morning and in the evening (Lugala, Uganda).

Glossina pallidipes is easily caught by trapping. Mare females than males are caught in traps. The Langridge, Moloo and Challier-Laveissiere traps are more effective in catching G. pallidipes, than fly-round patrols.

Different methods of sampling catch different parts of the fly population (see Volume I, 7.10.1). Flies caught on a fly-round are younger than flies caught at a tethered ox, and these are younger than flies caught in traps. While traps catch more females than males, many more males than females come to a fly-round patrol.

A trap that is left for months in the same position catches fewer flies as the weeks pass by, even if the traps are remade using new material. But on placing the traps in new positions, the catch increases greatly.

A rate of dispersal of about 140 m per week within a G. pallidipes fly belt has been estimated.

2.4.8 Epidemiology and control Glossina pallidipes is a very important vector of animal trypanosomiasis.

Glossina pallidipes can also be important in spreading Rhodesian sleeping sickness. Sometimes it is the only vector infesting a sleeping sickness area, but even when it lives together with greater numbers of G. morsitans it may still be important because:

  1. Glossina pallidipes depends heavily on the bushbuck for its food

  2. Bushbuck is known to be a reservoir for T. rhodesiense

  3. Bushbuck often lives in fairly close association with man.

Cattle can also be very important as a reservoir of T. rhodesiense, in G. pallidipes areas (Alego, Kenya).

In Lambwe Valley (Kenya) it was thought that G. pallidipes feeding on game animals, especially bushbuck in thickets, kept T. rhodesiense transmitted to natural hosts. Contact between man and cattle on the one hand, and the tsetse and wild host on the other, could cause outbreaks of sleeping sickness.

Total trypanosome infection rates in G. pallidipes vary according to area but not significantly to season.

At Lugala (Uganda), congolense and vivax mature infections began to appear in flies about 11–15 days old and reached a high level (17% and 6% respectively) in flies about 40 days old. Brucei infections did not appear until flies were about 43 days old.

Insecticidal control schemes directed against G. pallidipes (Kenya) have included: ground spraying of dieldrin in the Lambwe valley outside the game reserve, in the Lake Victoria basin; and experimental aerial spraying (both by helicopter and fixed-wing aircraft) using dieldrin.

Deliberate bush clearing as well as human settlement has greatly assisted the eradication of G. pallidipes from very large areas of Kenya.

2.5 ECOLOGY OF GLOSSINA AUSTENI

2.5.1 Environment The species is distributed along the eastern side of Africa from Somalia to South Africa. It is limited mainly to regions within about 200 km of the coast, and up to altitudes of 900 m.

The main habitat is evergreen thicket. Dense secondary forest and sacred groves (Kenya) are also used. Abandoned plantations, for example of rubber, cloves and teak, may contain G. austeni.

2.5.2 Resting sites In Kenya, the fly uses the densest shade that is available in hot dry weather. It rests on the underside of horizontal branches, up to 1 m from ground level.

It also rests under curled-up dead leaves on the ground, in the forest.

2.5.3 Host animals The host animal most often fed upon by G. austeni is the bushpig. Nearly 60% of feeds are taken from this one species. Also important are man, cattle and duiker. The bushpig and duiker are selected because of their habit of sheltering in the same thickets as G. austeni.

2.5.4 Predators and parasites The elephant shrew (Petrodomus tetradactylus) may find and eat pupae of G. austeni. Thyridanthrax (Bombyliidae), mutillid wasps and certain other parasitic wasps have been bred from G. austeni pupae, but at very low rates (0.7%).

2.5.5 Behaviour This species attacks man silently, settling just behind the knee. However, it is not particularly attracted to man, which may make it difficult to survey even when it is thought to be present in an area. Using a bait ox gives much better results than using man alone.

Early morning and late afternoon times for surveys are recommended.

Flies may sometimes feed at night, especially in the hot dry season. This is unusual behaviour for tsetse.

2.5.6 Breeding sites Pupae may be found in the dry earth beneath overhanging rocks, as well as under fallen logs and under horizontal tree trunks. Pupae are commonly found around the base of cycads.

2.5.7 Epidemiology and control Glossina austeni can transmit cattle trypanosomiasis. Trypanosome infection rates may be quite high. In one area over 12% of G. austeni were infected with vivax group and congolense group; this was a rate higher than that found in G. morsitans, G. pallidipes or G. brevipalpis living in the same district (Sitatonga, Mozambique).

Where the local distribution of G. austeni is limited to waterside thickets, clearing has helped in control in the past.

Glossina austeni was exterminated (along with the more abundant G. pallidipes) from a game park in Zululand, South Africa, by means of an aerial insecticide campaign starting August 1946 and ending successfully two years later.


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