population dynamics of tropical arboreal Psocoptera (I nsecta) on two species of conifers in the Blue Mountains, Jamaica

(1) Between December 1970 and October 1971 53 179 individuals representing thirty-seven species of Psocoptera were collected from two conifer species, Podocarpus urbanii Pilger and Juniperus lucayana Britton, at Holywell Park (4000 ft, 1200 m), Hardwar Gap, Jamaica. (2) Podocarpus always supported more psocid species than Juniperus. (3) The psocid populations on both conifer species showed a bimodal temporal fluctuation of numbers, the peaks being in March and June. The population peaks on Podocarpus lagged 2 weeks behind those on Juniperus. (4) Caecilius equivocatus Mockford was the commonest psocid species on both conifers, forming 76% of the total number of individuals on Juniperus and 42% on Podocarpus. The data suggest that this psocid species migrates from Juniperus to Podocarpus when the populations on the former substrate become large. (5) Seven other psocid species are common and have been classified into three life-cycle patterns. (6) The diets of the eight common psocid species have been examined on both substrates. (7) Spatial separation, temporal separation or dietetic separation of species are shown to be possible factors which allow the coexistence of this large number of species.