INTRINSIC RATE OF INCREASE OVER DIFFERENT GENERATION TIME INTERVALS OF INSECT AND MITE SPECIES WITH OVERLAPPING GENERATIONS

The generation interval (G) (i.e., egg to first offspring egg) for an insect or mite species was considered as a biological time unit for arthropod species. For species with an oviposition period longer than G, the rate of population increase (r) can be determined at G, 2G, and maximal time as r(G), R2G, and r(m), respectively. The ratios, r(G)/r(m) and r2G/r(m), were used to evaluate the accuracy of r(G) and r2G in presenting the expected r(m). Calculation of r(G), r2G, and r(m) for Galendromus helveolus (Chant) revealed no significant differences between r(G), r2G, and r(m). Comparison of r(G), r2G, and r(m) from 40 sets of published data revealed between r(G)/r(m) = 0.954 (SD = 0.059, n = 40) and mean r2G/rm = 0.994 (SD = 0.01, n = 26). Only r(G) and r(m) were calculated for species that had a shorter oviposition period than 2G. At all studied case intervals, eggs laid after 2G of oviposition period did not contribute significantly to the calculated r(m) value. These results demonstrate savings both in time and money in designing experiments for determining the r(m) value for a species with a long oviposition period.