Seasonal Changes in Water Budgets in Two Free-Ranging Tenebrionid Beetles, Eleodes armata and Cryptoglossa verrucosa

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Abstract
Seasonal changes in water metabolism for two species of tenebrionid beetles, Eleodes armata and Cryptoglossa verrucosa, were investigated using laboratory and field studies. Dietary analyses indicated that E. armata consumed mostly vegetation (>95%), while C. verrucosa was predominantly insectivorous (>60%). Laboratory water budgets showed that food was always the major component of water intake for E. armata fed spring and summer diets but that food accounted for only 18% of total water intake for C. verrucosa eating dried crickets. Neither animal maintained body weight on dry food. Fecal water content was correlated with dietary water content, while transpiration was the major route of water loss for both species. Field water influx, efflux, and metabolic water gain were measured with doubly labeled water ( ). Influx and efflux were higher in early summer for both species than in any other season, with E. armata always having higher flux rates. Surface-active C. verrucosa had higher rates of influx than did burrow-confined animals in summer, while the same was true for E. armata in spring and winter following rainfall. No difference in efflux rates between confined and free-ranging animals was apparent for either species. Net transpiration was the greatest avenue of water loss in all seasons for both species, but food, metabolism, or drinking could account for the majority of input depending on season. The data suggest that adult C. verrucosa are more xeric adapted than are E. armata.