INTRINSIC RATE OF INCREASE AND TEMPERATURE COEFFICIENTS OF THE APHID PARASITE EPHEDRUS CALIFORNICUS BAKER (HYMENOPTERA: APHIDIDAE)

The demographic statistics and the temperature requirements for development of Ephedrus californicus Baker were determined under constant laboratory conditions. At 23 °C, females provided each day with forty 2nd-instar pea aphids, Acyrthosiphon pisum (Harris), lived for 13.4 days and laid 1193 eggs on average; the highest fecundity of any female was 1762 eggs. For an assumed population sex ratio of 1:1 males to females, the intrinsic rate of increase, r, was 0.371 females·female−1·day−1 when all eggs laid were counted. The lower temperature threshold for development, t, was estimated as 6.83 °C, and the time-to-adult, K, as 228.9 degree-days. The potential use of E. californicus in the biological control of the lupine aphid, Macrosiphum albifrons Essig, in England is considered.