DIGESTIBILITY STUDIES WITH CELLULOSE-U-C14 ON LARVAE OF PALE WESTERN CUTWORM AGROTIS ORTHOGONIA

To determine whether fifth instar larvae of the pale western cutworm, Agrotis orthogonia Morr., could digest cellulose, they were fed an artificial diet that contained cellulose-U-C14. Only 0·36 per cent of the carbon-14 ingested during the fifth instar was expired as CO2 and 1 per cent of that ingested was recovered in the insect bodies when the experiment concluded. Hence there is little if any cellulase activity in the gut of the cutworm. Because cellulose-U-C14 was not digested, it was tested as an index compound for indirect measurement of consumption and utilization of food. There was excellent agreement between results obtained with cellulose-U-C14 and the standard index material, chromic oxide. Because of the sensitivity of radio tracer techniques, use of cellulose-U-C14 as the index compound may permit measurements of food utilization to be extended to early stage larvae. © 1969.