Hostname: page-component-cd9895bd7-p9bg8 Total loading time: 0 Render date: 2024-12-26T18:26:18.740Z Has data issue: false hasContentIssue false
  • English
  • Français

Effect of host plant on moulting in the African armyworm Spodoptera exempta (Walk.) (Lepidoptera: Noctuidae) at constant temperature and humidity conditions

Published online by Cambridge University Press:  08 April 2017

Jacob G. Yarro
Jacob G. Yarro
Affiliation:
International Centre of Insect Physiology and Ecology (ICIPE), P.O. Box 30772, Nairobi, Kenya
Get access

Abstract

There are five caterpillar instars in the life cycle of Spodoptera exempta (Walk.) when they feed upon star grass, Cynodon dactylon (L.) Pers., maize, Zea mais L. and Kikuyu grass, Pennisetum clandestinum Chiov. at 25–30°C. When the temperature is 18°C, however, there was an additional instar in the cycle. Similarly extra instars are formed on Guinea grass, Panicum maximum Jacq., Setaria plicatilis (Hochst.) Hack, and a sedge, Cyperus maranguensis K. Schm. even when the temperature appears to be sufficiently high for normal development. Occasionally the additional sixth instar is also too small to pupate, in which case a seventh instar is formed. It appears that caterpillars on nutritionally inadequate host plants or those at low temperatures are being partially starved and must continue moulting until the appropriate size is attained or exceeded. Measurements of the head capsule widths or distances between the frontal clypeal setae suggest that only individuals reaching or exceeding a species specific threshold size pupate. Extra moults appear to be an adaptation to environmental fluctuations obtaining within the range of occurrence of S. exempta.

Keywords

African armywormhost plantshead capsule widthsdistance between frontal setaevariation in the number of instars
Type
Research Articles
Information
International Journal of Tropical Insect Science , Volume 6 , Issue 2 , April 1985 , pp. 171 - 175
Copyright
Copyright © ICIPE 1985

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

Brown, E. S. (1970) Control of the African armyworm, Spodoptera exempta (Walk.)—An appreciation of the problem. E. Afr. agric. For. J. 35, 237–245.Google Scholar
Brown, E. S., Betts, E. and Rainey, R. C. (1969) Seasonal changes in distribution of the armyworm, Spodoptera exempta (Walk.) (Lepidoptera, Noctuidae) with special reference to East Africa. Bull. ent. Res. 58, 661–728.CrossRefGoogle Scholar
Brown, E. S. and Swaine, C. (1966) New evidence on the migration of moths of the African armyworm, Spodoptera exempta (Walk.) (Lepidoptera, Noctuidae). Bull. ent. Res. 56, 671–684.Google Scholar
David, W. A. L., Ellaby, S. and Taylor, G. (1975) The viability of eggs of the African armyworm, Spodoptera exempta in laboratory cultures. Entomologia exp. appl. 18, 266–237.Google Scholar
Gilbert, L. I. and King, D. S. (1973) Physiology of growth and development: endocrine aspects. In The Physiology of Insecta (Edited by Rockstain, M.), Vol. 1, pp. 249–370. Academic Press, New York.Google Scholar
Hattingh, C. C. (1941) The biology and ecology of the armyworm (Laphygma exempta) and its control in South Africa. Dep. Agric. S. Afr. Sci. Bull. 217, 1–50.Google Scholar
Matthee, J. J. (1946) A study of the phases of the armyworm (Laphygma exempta Walk.). J. ent. Soc. sth. Afr. 9, 60–77.Google Scholar
Nijhout, H. F. (1975) A threshold size for metamorphosis in the tobacco hornworm Manduca sexta L. Biol. Bull. 49, 214–225.Google Scholar
Nijhout, H. F. and Williams, C. M. (1974) Control of moulting and metamorphosis in the tobacco hornworm, Manduca sexta (L). Cessation of juvenile hormone secretion as a trigger for pupation. J. exp. Biol. 61, 493–501.CrossRefGoogle ScholarPubMed
Odiyo, P. O. (1981) Development of the first outbreaks of the African armyworm, Spodoptera exempta (Walk.) between Kenya and Tanzania during the “off season” months of July to December. Insect Sci. Applic. 1, 305–318.Google Scholar
Patel, N. and Mathivan, K. (1969) Effect of hormones on RNA and Protein synthesis in the imaginal wing discs of the ricini silkworm. J. Insect Physiol. 15, 2141–2150.Google Scholar
Pipa, R. L. (1976) Supernumerary instars produced by chilled wax moth larvae: Endocrine mechanisms. J. Insect Physiol. 22, 1641–1647.Google Scholar
Podoler, H. and Klein, M. (1978) Distance between frontal setae. A new tool for determining caterpillar instars. J. not. Hist. 12, 341–347.Google Scholar
Rose, D. J. W. (1975) Field development and quality changes in successive generations of Spodoptera exempta Walk., the African armyworm. J. appl. Ecol. 12, 727–739.Google Scholar
Rose, D. J. W. (1979) The significance of low density populations of the African armyworm, Spodoptera exempta (Walk.). Phil, trans. R. Soc. Lond. B237, 393–402.Google Scholar
Wilde, J. de, Kort, C. A. D. de and Loof, A. de (1971) the significance of juvenile hormone titres. Mitt, schweiz. ent. Gesellsch. 44, 79–86.Google Scholar
Wigglesworth, V. B. (1970) Insect Hormones. Freeman, San Francisco.Google Scholar
Yarro, J. G. (1984) Survival and development of the African armyworm, Spodoptera exempta (Walk.) on some grass species (Gramineae). Insect Sci. Applic. 5, 1–5.Google Scholar