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OBSERVATIONS ON THE DESERT LOCUST IN EAST AFRICA FROM JULY, 1928 TO APRIL, 1929
Author(s) -
WILLIAMS C. B.
Publication year - 1933
Publication title -
annals of applied biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 80
eISSN - 1744-7348
pISSN - 0003-4746
DOI - 10.1111/j.1744-7348.1933.tb07442.x
Subject(s) - biology , habit , locust , predator , ecology , zoology , desert locust , predation , schistocerca , psychology , psychotherapist
SUMMARY. The paper deals with observations made on the desert locust in East Africa in 1928–9. Two broods were observed to develop between May, 1928 and April, 1929. Females slightly outnumbered the males in a number of random collections of adults. A list of plants eaten or avoided by the adults is given including species from 62 natural orders, of which 18 are represented by both edible and inedible species. Notes on the food plants of the hoppers are also included. Hoppers of the IVth and Vth stages were observed to have a maximum speed of about 1 / 4 mile per hour. The chief natural enemies seen were Stomatorrhyna lunata , a Dipterous parasite of the egg, and Sphex aegyptiacum , a predator on the adult locusts. The latter had developed a migratory habit and followed its host. No regular relation between direction of flight and direction of wind was observed. Trekking activity in swarms of hoppers of the IVth and Vth stages was most noticeable when the air temperature was above 15° C. Feeding was most general when the air temperature was above 10° C, and in the swarms observed, which were probably short of food, took place at almost any hour of the day. Continual observation of one band of hoppers throughout a whole day showed that the direction of movement was by no means constant. In fact two complete circles were made in the course of the day. Adult locusts were found to orientate head towards the sun when the black‐bulb temperature was 130° F. or above. Adult locusts were found to be insensitive to sounds such as the banging of tin cans (often used for scaring purposes) or the firing of a gun, but were much frightened by the noise of a file drawn down the edge of a saw. Railway trains were got through swarms of egg‐laying adults on the ground by having several boys running in front of the train at short intervals. This procedure frightened the locusts off the line and was much more successful than any system of brushes in front of the wheels. A few small‐scale experiments with poisoned bran showed no difference in effectiveness between sodium arsenate and sodium fluosilicate. A few individuals from a swarm of just hatched hoppers were kept in isolation until the last larval stage, but did not assume the pale colouring of the solitary phase. Dissections of adult females showed that the ovaries remained small (about 11 mm. long) as long as the locusts remained purple‐brown in colour.