Metabolic Scaling of Diapausing and Non-diapausing Pallid Emperor Moth, Cirina forda (Lepidoptera: Saturniidae)

Abstract

Allometric scaling of metabolic rate with body mass is a fundamental feature in insect 
physiology, yet the scaling relationship often varies across developmental stages due to 
differences in energy requirements, tissue composition, and metabolic regulation. This study 
examined the metabolic–mass scaling patterns in the non-diapausing larvae and diapausing 
pupae of Cirina forda, a widely distributed edible insect of significant ecological and economic 
importance. Metabolic rate was indirectly determined by measuring oxygen consumption (VO₂) 
through respirometry and carbon dioxide evolution (VCO₂) via titrimetric analysis. The 
relationship between body mass and metabolic rate was evaluated using Least Squares 
Regression (LSR) of log-transformed data (Log₁₀VO₂ vs. Log₁₀Mass). Analysis of Variance 
(ANOVA), t-tests, and coefficients of determination (R²) were employed to assess the 
goodness of fit, compare regression slopes, and evaluate the explanatory power of each 
regression model. All regression models yielded statistically significant results, indicating 
strong mass-dependent metabolic patterns across developmental stages. However, the slopes 
(scaling exponents) of regression lines for larval instars were not significantly different from 
one another, suggesting consistent metabolic scaling during larval development. In contrast, 
the slopes of regression lines for pupae aged 90–120 days were significantly different from 
earlier pupal stages, showing a marked decline in metabolic activity. Moreover, a significant 
difference was observed between larval and pupal regression slopes (t₄₂ = 4.32; P < 0.05), 
confirming distinct allometric relationships between the two life stages. The negative slopes 
observed in late pupae indicate a reduction in metabolic intensity with increasing mass, likely 
reflecting metabolic suppression during diapause. These findings highlight that the allometric 
scaling of C. forda is strongly stage-dependent, shaped by developmental physiology and 
adaptive energy conservation mechanisms. Understanding these patterns contributes to 
broader insights into insect bioenergetics and developmental ecology.