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CHAPTER 4
GLOSSINA SYSTEMATICS

The word systematics means the way in which animals and plants axe classified.

4.1 SPECIES AND SUBSPECIES

There are 22 different kinds or species of tsetse fly living in Africa today. Some of these species are divided again into subspecies, because of certain minor but constant differences in their anatomy. For most purposes, it is not necessary to distinguish between subspecies.

A list of all species and subspecies of tsetse would include a total of 30 names (see 4.6).

Amongst animals in general, all members of a particular species will breed successfully with each other, giving fertile offspring. But members of different species will not usually produce offspring, or if they do, the offspring will not be fertile. For example, when a male donkey breeds with a mare (female horse), the result is a mule, which is not fertile. In the same way, one species of Glossina will not breed successfully with another species. Also, there are nearly always visible differences between members of different species, so that one can tell each species apart just by examining them. Sometimes these differences are obvious, sometimes they have to be locked for carefully.

The members of the same species will usually look very similar to one another, although there will be differences to do with age and sex. When we are sorting out tsetse flies into different species, we do so according to their appearance. We may be able to sort them out by eye, or we may need the help of a hand lens or microscope (see Chapter 9 and 10.1).

4.2 GENUS AND SPECIES NAMES

The scientific name for the tsetse fly is Glossina. All tsetse flies are called Glossina, and all Glossina are tsetse flies.

Each different species of tsetse fly has its own species name added on to the name Glossina. We may speak of Glossina morsitans, Glossina fuscipes, Glossina palpalis and so on. If we are writing down the names of several species of tsetse fly, it is not always necessary to write the word Glossina in full, but it may sometimes be shortened to the initial letter. For example, we could write Glossina morsitans, G. fuscipes and G. palpalis, and it would be clear for the second two species that we are still referring to Glossina.

The first name, Glossina, is called the name of the genus, or the generic name. A genus (plural, genera) is a group of closely related species. The second name, e.g. morsitans, is the name of the species, or the specific name.

When we write the generic or specific name of an animal (or plant), it should be underlined (or if printed in a book, written in italics).

4.3 HOW A SPECIES GETS ITS NAME

When a fly is found that does not fit into any of the existing species it can be given a new name.

First it is examined very carefully to make sure it is a new species that has not previously been discovered. The points by which it differs from the other species are carefully described and drawn. The scientist who carries out this work can then choose a new name for the fly. He must not give it a name that has already been used for another species within the same genus. The name and the description are then published. He labels the specimen that he has described as a type specimen. Type specimens are usually kept in museum collections, not by private individuals.

Any other fly of the same species that may be discovered later must be called by the name given to that species.

The tsetse flies have been so well studied that it is unlikely that any new species remain to be found, although it is still possible. The last time a new species was reported was in 1955, when Glossina nashi was described and named.

4.4 FAMILY NAME

If there were any other genera closely related to Glossina, we would put them into the same family. But nowadays Glossina is regarded as being an isolated genus and it is usually put into its own family Glossinidae.

(Appendix I lists a number of other important families of flies that you should know about).

4.5 SPECIES GROUPS

The 22 different species of Glossina can be arranged into three species groups. The species groups differ in the construction of the male genitalia. These differences can be seen in fresh specimens using a xl0 hand lens (Figure 9.6), but they can be examined in much more detail using a microscope. There are certain differences between the groups in other parts of the anatomy also. These differences are described in Chapter 9.

4.6 LIST OF GLOSSINA SPECIES AND SUBSPECIES, WITH INTERNATIONAL SYMBOLS AND COLOUR REFERENCES

4.6.1 List of species and subspecies The following is a complete list of Glossina species and subspecies as currently recognised.

Morsitans group

Glossina langipalpis
Glossina pallidipes
Glossina morsitans morsitans
Glossina morsitans submorsitans
Glossina morsitans oentralis
Glossina swynnertoni
Glossina austeni

Palpalis group

Glossina palpalis palpalis
Glossina palpalis gambiensis
Glossina fuscipas fuscipes
Glossina fuscipes martinii
Glossina fuscipes quanzensis
Glossina tachinoides
Glossina pallicera pallicera
Glossina pallicera newsteadi
Glossina caliginea

Fusca group

Glossina nigrofusca nigrofusca
Glossina nigrofusca hopkinsi
Glossina fusca fusca
Glossina fusca congolensis
Glossina fuscipleuris
Glossina haningtoni
Glossina schwetzi
Glossina tabaniformis
Glossina nashi
Glossina vanhoofi
Glossina medicorum
Glossina severini
Glossina brevipalpis
Glossina longipennis

4.6.2 Symbols and colour references for tsetse flies

There are internationally accepted symbols and colours to be used to indicate the distribution of tsetse fly species when maps are being prepared.

These are given below:

SpeciesSymbolColour
Morsitans group
Glossina longipalpisPale red
G. pallidipesPale red
G. morsitansPale green
G. swynnertoniLight blue
G. austeniDark green
 
Palpalis group
G. palpalisBrown
G. fuscipesMauve
G. tachinoidesLight blue
G. palliceraOlive green
G. caligineaYellow
Fusca group
G. nigrofuscaOrange
G. fuscaOrange
G. fuscipleurisMauve
G. haningtoniDark green
G. schwetziBrown
G. tabaniformisLight blue
 
Fusca group
G. nashiPale green
G. vanhoofiPale green
G. medicorumPale blue
G. severiniBrown
G. brevipalpisMauve
G. longipennisYellow

4.7 MALE AND FEMALE SYMBOLS

Symbols used to indicate male and female are as follows:

male

female


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