Anti-Locust Bulletin (1959) 36, 1-49

Maud J. Norris (1959)
Reproduction in the red locust (Nomadacris septemfasciata Serville) in the laboratory
Anti-Locust Bulletin 36, 1-49
Abstract: The effects of crowding and isolation on the duration of hopper life and on adult weight, colour and morphometrics of Nomadacris septemfasciata are compared.
Locusts emerging as adults in the laboratory in England from April to July inclusive become sexually mature in a few weeks but those emerging in late summer and autumn have a prolonged imaginal diapause, comparable with, although shorter than, that of wild Nomadacris, and do not become mature until the following spring. Experiments, the results of which will be published elsewhere, have shown that the seasonal changes in day-length are responsible for the onset of diapause.
The changes in adult coloration and body-weight which occur between emergence and sexual maturation are described. Both diapause and non-diapause males and females increase their weight by about 50% during the first two or three weeks of adult life. After this, non-diapause females continue to increase in weight until oviposition, but the weight of diapause females remains stationary for several months, during which the ovaries remain undeveloped.
The quantities of grass (dry weights) eaten by the locusts at different periods of adult life were estimated. Although the consumption of diapause groups falls to a low level during the diapause period their consumption during early adult life does not necessarily differ from that of non-diapause groups.
The first pods in groups of non-diapause locusts were laid in from 36 to 63 days. The average interval between the first copulation and the first oviposition was 5.4 days. In diapause groups emerging in August and September the first pods were laid in from 190 to 235 days. The length of the diapause in groups emerging later in the autumn is shorter and the first pods were laid at the age of 134 to 183 days. The maturation time of groups emerging after December decreases progressively until April. The addition of mature males to diapause groups abbreviated but did not prevent diapause.
Maturation time in crowded adults tends to be shorter than that of adults kept in single pairs, whether the latter are isolated throughout life (solitaria) or during adult life only (isolated gregaria). This is mainly due to the synchronising effect of crowding which prevents delay in potentially late-maturing individuals. Density does not in general affect the incidence of diapause, which occurs seasonally in crowded and isolated individuals alike. In one preponderantly non-diapause batch, however, some isolated males entered diapause.
Egg-pods were laid by the mature females in both diapause and non-diapause groups at the rate of one pod in eight days. Crowded diapause females laid an average of 3.4 pods each and non-diapause ones an average of 4 pods. The difference is probably not significant. Both solitaria females and females isolated in pairs during the adult stage only (isolated gregaria) laid an average of about 6 pods each.
The average number of eggs in the pods laid by crowded females was 97. The number was slightly but significantly increased when the adults were kept in isolated pairs.
A high proportion of the first pods laid by non-diapause females are totally sterile. The incidence of such sterility is virtually confined to groups maturing before the age of seven weeks in which the males copulate before sperm is present so that the eggs are not fertilised. Since sperm begins to appear during the eighth week, - sterility from this source does not occur in diapause groups.
These do, however, sometimes lay unfertilised eggs when the females become mature before the males and oviposit before copulation. This occurs more often in isolated pairs than in crowded locusts, and sometimes in non-diapause solitaria although not in non-diapause crowds. A fairly large percentage of the eggs in fertile pods are also often sterile. No significant effect of density on such sterility was demonstrated.
The duration of adult life in the female is closely related to maturation time and averaged 69 days in non-diapause gregaria, 108 days in non-diapause solitaria and 256 days in diapause gregaria. Diapause males lived much longer than most non-diapause ones, but after maturity some of the latter lived for long periods and their total length of life was much less closely related to maturation time than that of the females.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)

Research topic(s) for pests/diseases/weeds:
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Nomadacris septemfasciata