Life history traits of Aphis gossypii Glover (Hom., Aphididae) reared on four widely distributed weeds

Variation in the life history traits of cotton aphids, Aphis gossypii Glover, reared on four widely distributed weeds, Ageratum houstonianum Mill, Bidens pilosa L. var. radiata Sch. Bip., Solanum nigrum L, and Spermacoce latifolia Aubl., were investigated. Cotton aphids were reared in the laboratory at 25degreesC. Each host plant had a distinct effect on aphid life history traits. Cotton aphids reared on S. nigrum had a significantly shorter developmental period, and age-specific fecundity peaked early. In contrast, cotton aphids reared on S. latifolia had a long developmental period and low age-specific fecundity. Cotton aphids that fed on B. pilosa and A. houstonianian displayed intermediate rates of growth and age-specific fecundity. Because the curves of age-specific fecundity (nz,) and age-specific net maternity (l(x)m(x)) on each host plant were close together, development time and the pattern of age-specific fecundity were the major factors determining the population growth potential of the cotton aphid on each weed. As a result, the intrinsic rate of population growth for aphids reared on S. nigrum was significantly higher (r(m) = 0.527 +/- 0.011) than it was for aphids reared on S. latifolia (r(m) = 0.194 +/- 0.012).