LIFE-HISTORY AND DEMOGRAPHY OF THE PREDATORY MITE, AMBLYSEIUS-LONGISPINOSUS EVANS

The life history and demography of Amblyseius longispinosus Evans were studied under laboratory conditions 25-28-degrees-C and 65-85% RH usi ng the red form of the twospotted spider mite, Tetranychus urticae Koc h complex as prey. The entire development from egg to adult averaged 1 02.5 h for both sexes with a survival rate of 90.0%. Immature females consumed more prey eggs than males, averaging 7.9 and 6.4 eggs/day, re spectively. The embryonic development time for male eggs was longer (a verage 45.2 h) than for female eggs (average 42.6 h). The average dura tion of succeeding stages did not differ between the sexes: larva, 15. 7; protonymph, 21.1; and deutonymph, 23.0 h. Larvae were not observed to feed. Statistically significant differences between sexes were note d with respect to consumption of the deutonymphs (female, average 4.0 +/- 0.2; male, average 2.9 +/- 0.3 eggs/day) but not of the protonymph s. Mating occurred on the same day as adult emergence and was repeated several times during the reproductive life. Egg laying started on the second day after emergence. Parameters relating to oviposition were: fecundity, gross (50.7) and net (43.3) eggs/female; hatchability, 99.6 % (gross) and 99.5% (net); the oviposition lasted at most 28 days and showed a peak in the first week. Net reproductive rate (R0) was 36.7 f emale offspring/female/generation time (T) of 9.0 days. The sex ratio was biased toward the females (71.9%), while the intrinsic rate of inc rease (r(m)) was 0.4 with a doubling time (DT) of 1.7 days. Males live d longer (36 days) than females (30 days) with a LT50 for males of 26 days and for females of 22 days.