Susceptibility of the leatherjackets Tipula oleracea and T-paludosa to soil flooding

A relation was found between temperature and the survival of larvae of Tipula oleracea and T. paludosa when submerged in tap water alone or on turf growing on a sandy loam flooded with still or disturbed water (experiments with soil always starting with freshly flooded soil). Larvae under water alone usually survived until they starved, whereas larvae submerged on soil died in a relatively short time. The periods of survival at a depth of 25 mm were the same for both large and small larvae of either species at any one temperature. The regression of log.-log. survival time on temperature was a straight line, mean arithmetic values ranging from about 5 h at 20 degrees C to 122 h at 0 degrees C. Survival times at 25 mm were not increased by disturbing the water and the times at greater depths were no different, providing the water was still. If the water was regularly disturbed then the greater the depth the longer the survival time at any one temperature. Survival times in deoxygenated water indicated that lethal conditions may not be entirely due to deoxygenation of the water.