Phase polymorphism in the red locust, Nomadacris septemfasciata (Orthoptera: Acrididae) in Madagascar

The crops of every continent of the world have been devastated from time to time by locusts or grasshoppers. To mention three major locust species, the Desert Locust (Schistocerca gregaria Forsk.) has caused havoc in a broad band of the world stretching from East Pakistan to Senegal and from the Mediterranean to Central Africa, the Red Locust (Nomadacris septemfasciata Serv.) has infested East, Central and Southern Africa, and the African Migratory Locust (Locusta migratoria migratorioides Rch. and Frm.) has plagued most of Africa south of the Sahara.What happens in one part of a plague area can significantly affect the situation in others and locust control is therefore an international problem, requiring international co-operation. Many of the threatened areas are countries where standards of living are not high and local agriculture is a mainstay of the economy; the regions are often inhospitable and lack modern roads, aerodromes and lines of communication.

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Enumerating Populations of Adults of the Red Locust, Nomadacris septemfasciata (Serville), in its Outbreak Areas in East and Central Africa

Bulletin of Entomological Research ◽

10.1017/s0007485300053608 ◽

1958 ◽

Vol 49 (2) ◽

pp. 273-285 ◽

Cited By ~ 12

Author(s):

C. C. Scheepers ◽

D. L. Gunn

Keyword(s):

Total Population ◽

Central Africa ◽

Nomadacris Septemfasciata ◽

Natural Mortality ◽

Red Locust ◽

Frequency Distributions ◽

Moving Vehicle ◽

The North ◽

Outbreak Area ◽

Outbreak Areas

SummaryA method is described of estimating the total numbers and frequency distributions of adults of the Red Locust, Nomadacris septemfasciata (Serv.), in outbreak areas of hundreds of square miles, based upon counting the numbers that fly up in a two-yard strip in front of a moving vehicle. The method has proved itself valuable for indicating both immediate and future requirements for killing the locusts, but it requires refining for some research purposes.By this method, the importance has been clearly shown of the process of congregation of scattered adult locusts in forming emigrant swarms that could start a plague. The locusts do not congregate but actually disperse just before laying eggs.The total population in part (189 sq. miles) of the North Rukwa Outbreak Area (a self-contained area of 253 sq. miles) in Tanganyika Territory has been followed for four years. There are indications that a small migrant swarm contains 5–10 million locusts, that a total population in the whole of the North Rukwa Outbreak Area of 20 million locusts is unlikely to yield a migrant swarm, but that 50 million locusts could readily do so.In 1953, after poor rains, no natural mortality was detected between July and October by the assessment methods described. In 1957, after good rains, natural mortality of 70–90 per cent. was revealed by the same methods, although the dry season was not fully covered by the assessments.

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THE PATTERNS OF DISTRIBUTIONS OF ADULTS OF THE RED LOCUST (NOMADACRIS SEPTEMFASCIATA SERVILLE) IN AN OUTBREAK AREA

Entomologia Experimentalis et Applicata ◽

10.1111/j.1570-7458.1963.tb00609.x ◽

1963 ◽

Vol 6 (2) ◽

pp. 123-132 ◽

Cited By ~ 2

Author(s):

P. M. SYMMONS

Keyword(s):

Nomadacris Septemfasciata ◽

Red Locust ◽

Outbreak Area

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Density Distributions of Hoppers of the Red Locust, Nomadacris septemfasciata (Serv.) (Orth., Acrid.), in Relation to Control by Insecticides

Bulletin of Entomological Research ◽

10.1017/s0007485300053785 ◽

1958 ◽

Vol 49 (3) ◽

pp. 467-478 ◽

Cited By ~ 5

Author(s):

C. C. Scheepers ◽

B. J. Eyssell ◽

D. L. Gunn

Keyword(s):

Population Distribution ◽

Egg Laying ◽

Control Measures ◽

Nomadacris Septemfasciata ◽

Red Locust ◽

Density Distributions ◽

Outbreak Area ◽

Observation Area ◽

The Mean ◽

Insecticide Control

In continuation of a study of the process of swarm formation in the Red Locust, Nomadacris septemfasciata (Serv.), to enable rational plans for control measures to be made, the population distribution of about 44½ million hoppers of the Red Locust was investigated in an observation area of 1,052 acres in the Iku outbreak area of the Rukwa Valley, Tanganyika Territory, from 18th January to 24th February 1957. to see if the hoppers showed a tendency to concentrate, which would have the effect of producing, immediately after the last moult, adult swarms from hoppers that were originally more scattered. From 25th January onwards, the estimated population remained constant in numbers. Densities over 50 per sq. yd. were unusual and, taking any continuous infestation over one per sq. yd. as a band, the mean density of hoppers in bands was 15 per sq. yd. There was a tendency for such bands to become larger by fusion and for the area quite free from locusts to increase slightly but the number of dispersed locusts increased. There would therefore have been no advantage in withholding insecticide control in the hope of attacking denser and more economical targets. Nevertheless, such populations have to be controlled.In the Red Locust, under the conditions described, it seems probable that the behaviour of the young adults is most important in the formation of dense swarms, while in certain other species but not in the Red Locust, concentrated egg-laying and the behaviour of the hoppers are also important.Investigations are required on more economical enumeration of patchy gregarious distributions.

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