Interactive effects of density and water sodium concentration on insect larvae inhabiting treeholes

Michael J. Baltzley, Christopher J. Paradise, and William A. Dunson

Abstract

There is an inverse correlation between sodium concentration and densities of certain insects in natural treeholes. This field correlation suggests that sodium might be a limiting resource. The relationship between the growth of the culicid mosquito A. triseriatus, held alone, and the scirtid beetles H. pulchella and P. discoideus, to water sodium and population density was studied here in a laboratory experiment. Two initial levels of sodium (0, 300 mM) and three levels of insect density (0, 100, 200/L) were used. At low densities, microcosms high in [Na] produced significantly larger adult A. triseriatus than those low in [Na]. Conversely, scirtids grew slower in microcosms high in [Na]. At high density, dry masses of adult A. triseriatus and larval scirtids were significantly smaller than at low density. High densities were also associated with longer emergence time, a lower percentage survival, and a lower percentage emergence of adult male A. triseriatus. High densities of scirtids decreased the [Na] concentration of the water in the microcosms. These results indicate that the negative effects of increased density are not alleviated by high [Na]. Yet, mosquitoes at low density grow faster at high sodium. Some treehole insects may be particularly susceptible to the effects of sodium lack since inland rainwater and stemflow that fill the treehole are deficient in this essential solute.

Interactive effects of density and water sodium concentration on insect larvae inhabiting treeholes

Michael J. Baltzley, Christopher J. Paradise, and William A. Dunson

Abstract

Key words Aedes triseriatus density dependence Scirtidae sodium treeholes

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