TURNOVER OF THE GUT CONTENTS (TRACED WITH INULIN-CARBOXYL-C-14), TRITIATED-WATER AND NA-22 IN 3 STORED PRODUCT INSECTS

On food labelled with inulin-carboxyl-14C, adults of four species of insects accumulated an amount of 14C comparable to that in a weight of food solids equal to their loss of body solids during the first days of fasting. All of this 14C was subject to clearance from the body and could be accounted for in the cage debris. The time dependence for clearance of the 14C while held on unlabelled food was, in several tests, comparable to that for its accumulation from the labelled food; and the time dependence for its clearance while fasting was similar to that of the body solids loss. In contrast to the 14C of inulin, 22Na was concentrated in the body; its clearance was that of a first-order process from a single compartment, but the clearance was slower on food to which NaCl had not been added and very slow while fasting. The rate of solids ingestion was calculated as the product of the weight of body solids lost while fasting and the fractional rate of 14C turnover while feeding. The following data from tests at 20°C in 85% r.h. are representative. A Sitophilus granarius adult of 4.1 mg fresh weight ingested 170 μg of tapioca solids each day, of which the weight of carbon is only slightly more than the 55 μg of carbon lost each day as CO2: its 1.6 mg of body water had a turnover of 12%/day to which food moisture contributed 17%, metabolic water production (identified with the molar rate of CO2 production) contributed at most 39%, and diffusion contributed atlleast 44%. An Oryzaephilus surinamensis adult of 550 μg fresh weight feeding on oatflakes ingested 47 μg of solids per day while 9.5 μg was lost as carbon with CO2: its 260 μg of body water had a turnover of 34%/day to which ingested moisture contributed 10%, metabolic production 15% and diffusion 75%. The booklouse Liposcelis bostrychophilus of 40 μg fresh weight ingested 1.25 μg of yeast solids each day while the carbon loss with CO2 was only 0.18 μg/day and eggs were produced. Its 30 μg of body water had a turnover of 40%/day to which ingested moisture contributed 4%, metabolic production 5%, diffusion approximately 40% and physiological absorption of vapor nearly 50%. A few data were also reported for Sitophilus oryzae. © 1978.