Abstract
From samples taken at regular intervals from populations of Chortoicetes
terminfera (Walk.), it was found that the time of onset of sexual maturation in the
female was consistently associated with a sharp drop in daily air temperature and not
invariably with rainfall. As such temperature changes are indicative of air mass changes
and the occurrence of cold fronts, the locusts began to mature with, or just prior to, rain.
The period required for maturation was approximately 12 days and the frequencies
of occurrence of gravid females in populations underwent cyclic fluctuations.
It is, therefore, possible to predict the time of laying from a knowledge of the time of
onset of maturation. Moreover, the sequence of successive layings in populations
could be determined from cosine curves with periods of 12 days.
Females of the second generation of the locust "season" (January-March) laid
more egg pods than those of the first generation (September-December of the previous
year). This may partly explain the frequent occurrence of temporary declines in swarm
numbers and the collapse of outbreaks during the January-February period.
In both swarming and non-swarming populations synchronization in the time
of completion of a cycle of maturation by females was poor. However, the social
behaviour of gregarious populations ensures that the egg pods laid by females of
different physiological ages, i.e. those that reached maturity on different days, are
concentrated in the one oviposition site. This maintains continuity in the swarming
cycle because concentration of the egg pods results in the subsequent crowding of the
nymphs during the hatching period.
Subject
Animal Science and Zoology,Ecology, Evolution, Behavior and Systematics
Cited by
26 articles.
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