Behavioural ecology of the African armywonn, <i>Spodoptera exempta</i> (Walker) (Lepidoptera: Noctuidae); evidence of successive generations from Kenya

Khasimuddin, Syed; Lubega, M. C.

doi:10.1017/s0007485300017740

Cited by 12 publications

(8 citation statements)

References 3 publications

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“…Field and laboratory evidence supports this interpretation for the African armyworm Spodoptera exempta. There are few reports of successive generations in the same place (Hattingh, 1941;Rose, 1975;Khasimuddin and Lubega, 1979) and Rose suggests these result from suppression of emigration by rainfall soon after moth emergence. If, as Gatehouse (1986) suggested, emigration is the optimal strategy irrespective of conditions in the current habitat, proximal environmental cues predicting its suitability are irrelevant, and migratory capacity can then only be determined genetically.…”

Section: Evolution Of Migratory Strategiesmentioning

confidence: 99%

GENETICS OF PRECALLING PERIOD IN THE ORIENTAL ARMYWORM,MYTHIMNA SEPARATA(WALKER) (LEPIDOPTERA: NOCTUIDAE), AND IMPLICATIONS FOR MIGRATION

Han

Gatehouse

1991

Evolution

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Migration in insects usually occurs prereproductively so the precalling period, between emergence and the first release of pheromone, determines the number of nights over which females of migrants such as Mythimna separata can express their migratory potential. Precalling periods (PCP's) ranged from 3 to 21 nights in F females from insects collected in the field in eastern China. As technical problems precluded the use of a sib-analysis design, the genetic basis of this variation was investigated by analysis of the correlation between daughters' and mother's PCP's and by selection in isofemale lines followed by reciprocal crosses. The results of these analyses indicated that PCP is strongly influenced by genes located on the X chromosome, inherited from the male parent in Lepidoptera. Genetic regulation of migratory potential, of which PCP is a crucial component, can be expected to evolve in tropical species such as Mythimna separata, whose larval habitats are associated with unpredictable tropical rainfall. This species has no preimaginal diapause but makes regular seasonal incursions every spring and early summer to high temperate latitudes at which it cannot overwinter. Where migrants are carried by winds, as occurs in these migrations, the predominantly poleward winds at this time of year must create a genetic cline across latitude, in which migratory potential of the summer populations founded by the migrants increases with increasing latitude. We suggest that X-linkage of genes influencing PCP may reduce the genetic load associated with this polymorphism by reducing the frequencies of inappropriate PCP genotypes in these summer populations. Thus, in autumn when winds are predominantly northerly, fewer individuals at any latitude will lack the capability to make the return journey southward. Some support for this model is provided by the observed distributions of PCP's of F females from moths collected in the field in central and northern eastern China. If X-linkage of genes influencing PCP contributes to the stability of these migratory cycles, it can be expected in other species with similar migratory strategies.

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Section: Evolution Of Migratory Strategiesmentioning

confidence: 99%

GENETICS OF PRECALLING PERIOD IN THE ORIENTAL ARMYWORM,MYTHIMNA SEPARATA(WALKER) (LEPIDOPTERA: NOCTUIDAE), AND IMPLICATIONS FOR MIGRATION

Han

Gatehouse

1991

Evolution

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Section: Evolution Of Migratory Strategies Of Mythimna Separata and Omentioning

confidence: 99%

Genetics of Precalling Period in the Oriental ArmyWorm, Mythimna separata (Walker) (Lepidoptera: Noctuidae), and Implications for Migration

Han¹,

Gatehouse²

1991

Evolution

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“…Moths migrate downwind to be subsequently concentrated in regions of rainfall where there are likely to be flushes of grasses for young caterpillars. Consecutive outbreaks rarely occur in one place and when they do, this is attributed to local rain at the time of moth emergence (Rose 1975;Khasimuddin and Lubega 1979). Permanent or semi-permanent breeding sites in marshes or flood plains have not been found.…”

Section: Discussionmentioning

confidence: 99%

The bionomics of the African armyworm Spodoptera exempta in relation to its status as a migrant pest

Rose

Dewhurst

Page

1995

Integr Pest Manag Rev

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A multidisciplinary study was undertaken on the bionomics of the African armyworm in eastern Africa as a basis for the development of control strategies for this important pest of cereal crops and pastures. Relevant findings from studies on seasonal distribution, migration, field infestations and population cycles are reviewed in relation to understanding the causes for the onset and spread of armyworm outbreaks. It is concluded that the onset of the first outbreaks of an armyworm epidemic is caused by oviposition at high density by moths concentrated by wind convergence at storm outflows. The sources of these moths seem to be low-density populations which survive from one season to the next at sites receiving unseasonable rainfall. Some areas in Tanzania and Kenya are particularly prone to early outbreaks which are potentially critical for the initiation of a subsequent spread of outbreaks downwind throughout eastern Africa. These areas have low and erratic rainfall, and are near the first rising land inland from the coast. Below average rainfall prior to the development of outbreaks increases the probability of their occurrence. Their subsequent spread is enhanced by storms downwind which concentrate moths in flight and by sunshine during caterpillar development. Persistent wet weather reduces the spread of outbreaks. This study demonstrates the importance and value of developing and implementing a long-term monitoring system over a large region, in this case in Africa, not only for the generation of data used by the forecasters for the prediction and location of possible outbreaks, but also for obtaining a clearer understanding of the epidemiology of a highly mobile pest.

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Behavioural ecology of the African armywonn, Spodoptera exempta (Walker) (Lepidoptera: Noctuidae); evidence of successive generations from Kenya

Cited by 12 publications

References 3 publications

GENETICS OF PRECALLING PERIOD IN THE ORIENTAL ARMYWORM,MYTHIMNA SEPARATA(WALKER) (LEPIDOPTERA: NOCTUIDAE), AND IMPLICATIONS FOR MIGRATION

GENETICS OF PRECALLING PERIOD IN THE ORIENTAL ARMYWORM,MYTHIMNA SEPARATA(WALKER) (LEPIDOPTERA: NOCTUIDAE), AND IMPLICATIONS FOR MIGRATION

Genetics of Precalling Period in the Oriental ArmyWorm, Mythimna separata (Walker) (Lepidoptera: Noctuidae), and Implications for Migration

The bionomics of the African armyworm Spodoptera exempta in relation to its status as a migrant pest

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