The biology and population dynamics of Icerya purchasi Maskell (Homoptera: Margarodidae)
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1969
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University of Hawaii at Manoa
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Abstract
The biology of Icerya purchasi Maskell was studied on Desmodium plants. The average durations of the different stages were: egg stage. 15.4 days; crawler stage, approximately 4 to 5 days (based on the studies conducted on the settling rates); second instar, 9.9 days; third instar, 12.3 days; preovipositional stage, 8.2 days; and the mature female ovipositional stage, 39.1 days. The development period from egg to mature female was about 60 days, and the cumulative longevity from egg to death was about 99 clays.. The average fecundity per mature female was 678.6 eggs. I. purchasi infests some 51 host plants in Hawaii of which 26 were reported during this study. Behavioral studies of crawlers showed that the settling rates of 4 and 5 day old crawlers were significantly higher than those of other ages. Distribution of I. purchasi in the field showed that 59 per cent of the scales settled on the leaves and 41 per cent settled on the stems. The first instar immatures predominantly settled on the leaves near the top of the plant. The second instar occurred in about equal numbers on the stems and leaves, and the third instar and adult scales settled predominantly on stems near the base of the plant. studies on the life history of Rodolia cardinalis (Mulsant), a predator of I. purchasi, showed that the average duration of the stages were: egg to adult, 25 days; egg stage, 4.5 days; larval stage (including the pre-pupal stage), 15.9 days and the pupal stage, 4.6 days. Field studies in Desmodium fields on the seasonal abundance of I. purchasi showed a period of high seasonal abundance from July to November, 1967, peaking in August and September, and a low population during December, 1967 to June, 1968. Studies on the suppressive abilities of the predator, g. cardinalis, and the parasite, Cryptochaetum iceryae (Williston), on field populations of I. purchasi were evaluated. No parasitization of the first instar of I. purchasi was found. The per cent parasitization of the susceptible stages in Desmodium fields was: second instar, 3.3 - 5.2 per cent; third instar, 10 - 18.5 per cent; and mature females, 14.8 - 25.2 per cent. There was a lag between the peak of predator and prey populations which occurred during October and November.
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Cottony-cushion scale
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Theses for the degree of Doctor of Philosophy (University of Hawaii (Honolulu)). Entomology; no. 230
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