We manipulated the amount of food and water (soil moisture) available to natural populations of larval tiger beetles in Arizona. Supplemental food increased survivorship of first instars to the second instar in all species in at least one of two years. Supplemental soil moisture usually increased, but sometimes decreased, survival of first instars. Interaction of food and water treatments was significant in a few cases, but the nature of the interaction varied greatly among species and years. Significant mortality of first instars from natural enemies occurred, and may explain the anomalous cases of first—instar survival with food exclusion (since enemies were also excluded by this treatment). Food supplementation increased first—instar—to—adult survivorship for all species and third—instar—to—adult survivorship for most species; in contrast, water supplementation had no effect on most species. Food manipulation, but not water manipulation, also affected development time or size of adults (usually both) for all seven species tested. Supplemental food produced larger adults and resulted in more rapid maturation. Reduced food resulted in delayed development, and this usually resulted in death. The results of this study provide one of the few cases in which simultaneous effects of two major ecological factors have been analyzed for a large set of similar species in an array of habitats. The prevalence of food limitation and the frequent lack of a detectable consistent interaction between food availability and water availability in this system indicate that food limitation and resource competition may be the dominant factors controlling these organisms.

The effect of fluoride on the food and dietary water intake and utilisation were studied in final instars of silkworm, Bombyx mori L. race NB₄D₂ fed ad libitum with mulberry leaves treated with sodium fluoride at concentrations of 25 ppm, 50 ppm and 75 ppm. The larval duration increased by two days while food consumption, assimilation rate, assimilation efficiency, feeding and metabolic rates increased significantly in all the treated larvae. On the other hand, the amount of faeces produced, food conversion, conversion rate and conversion efficiencies decreased significantly in all the treated batches when compared to controls. The water intake and utilisation parameters increased significantly while rate of water loss through faeces, water retained in the body and retention efficiency decreased in all the fluoride-treated silkworms. The factors responsible for these changes in treated batches are discussed in relation to the effect of fluoride on cocoon and shell weights.

Some hemipteran xylem and phloem-feeding insects have evolved specialized alimentary structures or filter chambers that rapidly transport water for excretion or osmoregulation. In the whitefly, Bemisia tabaci, mass movement of water through opposing alimentary tract tissues within the filter chamber is likely facilitated by an aquaporin protein. B. tabaci aquaporin-1 (BtAQP1) possesses characteristic aquaporin topology and conserved pore-forming residues found in water-specific aquaporins. As predicted for an integral transmembrane protein, recombinant BtAQP1 expressed in cultured insect cells localized within the plasma membrane. BtAQP1 is primarily expressed in early instar nymphs and adults, where in adults it is localized in the filter chamber and hindgut. Xenopus oocytes expressing BtAQP1 were water permeable and mercury-sensitive, both characteristics of classical water-specific aquaporins. These data support the hypothesis that BtAQP1 is a water transport protein within the specialized filter chamber of the alimentary tract and functions to translocate water across tissues for maintenance of osmotic pressure and/or excretion of excess dietary fluid.