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A mathematical model has been developed for estimating the consumption of canopy vegetation by insects. The model divides canopy leaves into age classes according to time of leaf emergence. Periodic measurements were made of gross leaf area and h ole area initiated by insect consumption for each generation. Gross area distributions were used to determine empirical growth functions for the canopy vegetation. The rate of change in hole area is a function of both insect consumption and subsequent hole expansion due to leaf growth. The hole expansion rate was determined empirically by punching holes in known area in growing leaves and correlating hole expansion with leaf growth. From these relationships, a linear differential equation was derived to describe the dynamics of insect grazing in the canopy. This model was used to interpret the effect of insect herbivory on the dry matter and nutrient cycles in a Liriodendron tulipifera forest. Average herbivorous insect consumption over 3 years was equivalent to 2.6% of the net primary production of foliage biomass but represented an annual loss of 7.7% in photosynthetic surface area.
Reichle et al. (Sat,) studied this question.