Population density, survival, growth, and development of the American cockroach |
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| Authors: | D R Wharton J E Lola M L Wharton |
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| Affiliation: | 1. Institut d''Electronique Fondamentale, UMR CNRS 8622, Univ. Paris-Sud, 91405 Orsay, France;2. Hitachi Cambridge Laboratory, J. J. Thomson Avenue, CB3 OHE Cambridge, United Kingdom;3. Institut Jean Lamour, UMR CNRS 7198, Univ. de Lorraine, F-54506 Vandoeuvre-les-Nancy, France;4. IMEC, Kapeldreef 75, 3001 Leuven, Belgium;1. Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, 84112, USA;2. DENLABS, Draper, UT, 84020, USA;1. Servicio de Dermatología, Hospital Ramón y Cajal, Universidad de Alcalá, Madrid, Spain;2. Servicio de Medicina Preventiva y Salud Pública, Hospital Ramón y Cajal, Madrid, Spain;1. Director of Basic Research, InBio, 700 Harris Street, Charlottesville, VA 22903, USA;2. Professor of Medicine, Ribeirão Preto Medical School, University of São Paulo, Av. Bandeirantes 3900, Ribeirão Preto, SP 14049-900, Brazil;1. Nursing Research Center, Faculty Member, Golestan University of Medical Sciences, Gorgan, Iran;2. Student Research Committee, Neyshabur University of Medical Sciences, Neyshabur, Iran;3. Department of Nursing, Faculty Member of Neyshabur University of Medical Sciences, Neyshabur, Iran;4. Department of Anesthesia and Operating Room, Faculty Member of Neyshabur University of Medical Sciences, Neyshabur, Iran;5. Department of Environmental Health Engineering, School of Health, Isfahan University of Medical Sciences, Isfahan, Iran;6. Department of Environmental Health Engineering, Neyshabur University of Medical Sciences, Neyshabur, Iran |
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| Abstract: | The mortality rate of larvae of Periplaneta americana increases with increasing population density. The mortality curve is not linear but cascading and, like growth, mortality alternates with ecdysis. Three major phases of mortality are recognized: the first, with a high mortality rate during the first to the sixth week; the second, of brief duration and low mortality, during the sixth to the ninth week; and the third, of moderately high mortality which persists until development is completed. The mortality phases are dependent respectively on (1) a maximal increase in the instantaneous percentage rate of growth and a high frequency of ecdysis, which expose the larvae to injury and high mortality when in groups, (2) a slowing down of the growth rate, and (3) sexual development and continuing growth in the last instar associated with the metamorphosis of the larva to the adult. The data support the concept of a homology between the last larval instar of the hemimetabolous insect and the pupal stage of the holometabolous species.Isolation retards development of larvae and exerts its retarding influence at all stages of growth. In the present experiments the optimal density for growth of larvae is about 25.The average weight of adult insects tends to decrease with an increase in the population density of the larvae. On the other hand, the weight-time curve of emergent adults varies with density of the group.The results indicate the presence of a factor(s) which affects the rate of maturation of the insect throughout its development, which is a function of group size and is sex-dependent in that males are more sensitive to its influence.Cannibalism among larvae is observed chiefly with the young and is considered to be sanitary rather than predatory in character. |
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