. Animal Ecology. Animal ecology. niuil enough buoyancy is created to lift the spider and tarry it away, sometimes distances of hundreds of miles. Strong winds will often carry insects and even hirds great distances away from their usual courses. Crop pests may he blown North during the summer and cause damage, but may never become permanently established because they are killed by the northern winter cold. Hurricanes are an important means of colonizing islands far at sea with terrestrial species (Elton 1925, Darlington 1938). There are authentic records of rains of fishes and other aquatic s
. Animal Ecology. Animal ecology. niuil enough buoyancy is created to lift the spider and tarry it away, sometimes distances of hundreds of miles. Strong winds will often carry insects and even hirds great distances away from their usual courses. Crop pests may he blown North during the summer and cause damage, but may never become permanently established because they are killed by the northern winter cold. Hurricanes are an important means of colonizing islands far at sea with terrestrial species (Elton 1925, Darlington 1938). There are authentic records of rains of fishes and other aquatic species that were sucked up and transported appreciable distances by tornadoes (Gislen 1948). In studies done in England (Freeman 1946), it was estimated that the number of insects drifting through a rectangle 91 m (300 ft) high and 1610 m (1 mi) long amounted to 12,500,000 per hour. The number was highest during May, June, and Septem- ber, at temperatures above 18°C. The aerial popula- tion over the forests and swamps of Louisiana has been measured (Click 1939), by means of traps placed on the wings of airplanes, and found to average the following number of individuals per 1000 cubic meters of air: Altitude Davtime Night 6 m (20 ft) — 61 m (200 ft) — 152 m (500 ft) — 305 m (1000 ft) 610 m (2000 ft) 914 m (3000 ft) 524 m (5000 ft) Diptera were most numerous, followed during the daytime by Coleoptera, Homoptera, Hymenoptera, Araneida, Hemiptera, and others. Spiders and wing- less insects were greatly reduced in numbers at night because of the lack of vertical convection currents. The density of insects in the air depends on the di- urnal and seasonal activity rhythms of the animals to give them exposure to air currents in their terrestrial habitats. Those species tend to be most numerous that have the greatest wing area per unit weight, hence the greatest buoyancy. The insect population in the upper air is not distinct from that
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Keywords: ., bookcentury1900, bookcollectionbiodive, booksubjectanimalecology
