Use of faecal weight as an indicator of food consumption in some lepidopterans.

Correlation coefficients obtained between food consumed and feces defecated are highly significant in the larva of Achaea junta and other lepidopteran larvae tested. Different factors like species, stage of life, temperature, and food quality do not significantly affect the value of the correlation coefficient in the larvae tested. The reference value (i.e. the ratio between dry food consumed and dry feces weight) of 1.5 for the moths and 1.9 for the butterflies is suggested for use in the estimation of total food consumption in phytophagous lepidopterans, and its applicbility is discussed. In all tested cases, the correlation coefficients between food consumed and number of pellets defecated showed no significance, indicating the unreliablity of fecal count as an index of food consumption.