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To be sure that you have an adult Desert Locust, it will help to check both size and colour (see pages 20-25), but first determine the sex of your specimen.
As female locusts must dig a hole in the soil to lay their eggs, the tip of the abdomen (body) carries two pairs of short, hard, dark-coloured hooks. The end of the male abdomen is soft.
FIGURE Figure 9 Size of
adults
Females are usually larger than males. The following
measurements are for the distance from
the front of the head to the tip of
the folded wings.
Females: smallest 7 cm largest 9 cm
Males: smallest 6 cm largest 7.5 cm
These sizes are shown in Figure 9, and when you know whether your specimen is male or female check by laying the specimen on the appropriate figure.
BEWARE: if the size is not within the range of sizes given, the specimen is unlikely to be a Desert Locust
Young swarming adults are a pink colour which can vary from dark to light
Older but immature adults become browner.
As they become sexually mature they turn yellow. This yellow colour becomes particularly bright in males.
These colours are typical of individuals from swarms; if you find a single locust of these colours, it may indicate that there has been a swarm in the area, even though it was not seen.
REMEMBER: always report the colour of the locusts that you find
Non-swarming locusts may be found either singly or in small groups, or even in large numbers if spread over a large area. They usually fly at night and may occasionally be seen near camp lights.
Young non-swarming adults vary considerably in colour; they may be sandy coloured, brown or greyish (Figure 11). Like swarming locusts they gradually turn yellow as they become sexually mature. The yellow colour can be quite bright but solitary females are less bright in colour than those from swarms.
REMEMBER: a yellow locust is not necessarily from a swarm
Rainfall is very important for breeding. It provides water in the soil which the eggs need to absorb in order to complete development and it enables the desert vegetation, on which the hoppers feed, to germinate and grow.
Upland regions often receive more rain than surrounding lowlands. Run-off can result in suitable breeding sites in wadi beds downstream of areas where the rain has fallen.
Female locusts prefer to lay their eggs in sandy or silty soils. The soil must hold water for enough time to allow the eggs to develop.
Vegetation attracts adult locusts and provides a supply of food for the newly hatched hoppers.
Temperature affects the rate of development of eggs and hoppers. Lower temperature slows down the rate of development.
A good report should provide answers to the following four basic questions:
1. WHAT WAS SEEN?
2. WHEN WAS IT SEEN?
3. WHERE WAS IT SEEN?
4. WHO SAW IT?
The following notes explain what information should be included in your answers to the four basic questions.
To answer the questions and make an accurate report, you will have to observe the locust population and examine an individual, so that you may identify it from the illustrations and information given in this pocket book.
When you see locusts, always try to catch a live one or find a dead one.
If you have an insect-collecting net, it is easier to catch a sample.
Two other methods of collecting samples are to look in the radiator grille of a vehicle and also around any lights at night.
If you think you have seen a swarm, try to get close enough to see if it is composed of Desert Locusts. Many reported locust swarms have turned out to be groups of other kinds of insects, birds or even clouds of smoke or dust.
This question can be divided into three parts:
(a) What kind?
(b) How many?
(c) What were they doing?
(a) What kind?
ADULTS (winged) or HOPPERS (wingless)
In either case give some indication of the colour, and in the case of hoppers also state the instar by comparison with Figure 6 on page 14.
(b) How many?
Except when the number of locusts seen is very small, it will not be possible to give an exact answer to this question, but some general indication of size of the population can be given in descriptive terms. The following examples indicate some of the possibilities.
For winged adults: (i) dense swarm 2 km across; (ii) swarm
flying overhead for 2 hours; (iii) scattered adults seen for 3 km; (iv) 4
locusts seen around camp lights; (v) groups of adults flushed when walking
through a millet cultivation.
For hoppers: (i) 10 dense bands of marching
hoppers seen in a distance of 2 km, the largest band 50 m across; (ii) many
small (approximately 1 m wide) groups in 10 ha of cultivated patches; (iii) 3 or
4 hoppers in each clump of vegetation for 1 km, average 20 clumps per 100 m2.
(c) What were they doing?
Adults may be in high-flying swarms, sometimes visible many kilometres away, or they may be low flying or settled on bare ground or on bushes or trees.
The locust organizations are interested in the direction of movement of a swarm but, as different groups of locusts in a swarm may be flying in different directions, this can be difficult to determine. Always give the direction from which the wind is blowing as the whole swarm is likely to be moving with the wind.
If locusts are on the ground, it is particularly important to report if they are mating or laying. When mating, the bright yellow males sit on top of the paler yellow females. When there are many locusts the males also remain on the females while they are laying, but if there are only a few locusts the sexes may separate. When laying, the females make a hole in the soil with the tip of their body (abdomen).
In the case of hoppers it is less important to report what they are doing.
If a locust population, either of adults or hoppers, is seen in a crop, this should always be reported.
Give the time as well as the date when the locusts were seen. It is important to state whether you saw adults by day or at night.
Remember that even with maps and gazetteers it is not possible to locate the name of every small village and grazing area. Therefore try to fix the position of your observation with reference to some well-known place, for example, 2 km from the sea, 50 km south of Jeddah; 30 km south of Bikaner. Latitude and longitude are the ideal methods of fixing a report if you have a map, but always include a reference to a well-known place as well.
Remember that the locust organizations plot your report on a map
Your name and address should be included for two reasons:
(i) your report may be particularly important to the locust organization you informed (see page 35) and an official may wish to contact you on special points of interest;
(ii) all reports sent to the Emergency Centre for Locust Operations of the Food and Agriculture Organization of the United Nations, Rome, are recorded in the name of the informant.
1. What was seen?
Were the locusts adults or hoppers? If they were hoppers, what was their instar?
What colour were the locusts?
How many locusts were seen? Were they in swarms or bands or single individuals? In which direction were they moving?
What were the locusts doing? Were they flying, marching, mating or laying eggs? What were they eating?
2. When did you see them?
Was it daytime or night? Which date did you see them?
3. Where did you see the locusts?
Do you know the map reference? Can you give a rough guess of the distance from a well-known place?
4. Who saw them?
Please give your name and address when making a report.
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