A computer model of the growth of larval dragonflies

A computer model was constructed using the bioenergetics data of J.H. LAWTON ( Hydrobiologia 36 1970: 33-52; J. anim. Ecol. 39 1970: 669-684, 40 1971: 395-423 ,Freshwat. Biol. 1 1971: 99-111) on Pyrrhosoma nymphula. Model predictions of the growth of an individual dragonfly were compared to Lawton’s data on length to test the model. Comparisons were also made between model predictions and field, literature, and laboratory data for Deep Creek, Oneida County, Idaho, USA, dragonflies, specifically Argia vivida, to test the generality of the model. Initially the model equations could not reproduce Lawton’s data, but when production and consumption were reduced in the winter months (temperature < 7°C), the results were within a mean 10% error of Lawton’s original data. Predictions for growth over the complete life cycle were also made with a starting date and initial length as inputs. Laboratory experiments with A. vivida, done as part of this study, provided data for tests of the model’s ability to make precise short-term predictions. In all but one case presented here, the predictions were statistically different from the observed even when equations specifically for A. vivida were used. However, the model as used for Lawton’s data did compare well with the field data for the whole life cycle of A. vivida. Finally, comparisons were made between P. nymphula, A. vivida, Enallagma anna, Ophiogomphus severus and Diplacodes trivialis which showed that differences in energy budgets can be related to differences in life histories.