The Ecology of Callosobruchus analis (Coleoptera: Bruchidae): Morphometrics and Energetics of the Immature Stages

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Abstract
The larvae of C. analis (F.) develop within the cotyledons of a number of pulses. Dwarf green peas [Pisum sativum] were selected as the host in a study of the morphometrics and energetics of the larvae, pupae and callow adults of this species. Peas containing a single larva were held at 30.degree. C and 70% r.h. [relative humidity]. They were divided into 6 groups of about 30. One group was dissected every 8-10 days. The head widths, body lengths and live and dry weights of the larvae were recorded. Production was measured from those data. The last group of peas to be dissected had been X-rayed at weekly intervals during the larval development period. Consumption and production were estimated from radiographs. The respiration rates of the insects were measured with a Gilson respirometer before the peas were dissected. The energy content of each stage was determined with a Phillipson microbomb calorimeter. Larvae pass through 5 instars in the pea. The relationships between dry weight and length and dry weight and live weight were of the expected form. The duration of each instar was determined by combining the data from direct observations and the radiographs. The energy components of the budgets for larvae at the mid-point of the final larval instar were: consumption (C) = 43.7 cal (183.0 J), production (P) = 20.4 cal (85.4 J), respiration (R) = 17.9 cal (74.9 J), egesta (FU) (determined by difference) = 5.4 cal (22.7 J) and assimilation (A) = 38.3 cal (160.3 J). The overall energy budget for larvae, including the non-productive tunnelling phase of the 5th instar, was: C = P + R + FU; 57.0 = 28.4 + 20.4 + 8.6 cal; 238.4 = 118.8 + 85.3 + 36.0 J; A = 48.8 cal (204.3 J). A comparison of the P to R ratio (141.8%), assimilation efficiency (85.0%), net biological efficiency (58.7%) and gross biological efficiency (49.9%) with those of other arthropods indicates that legume seeds are a favorable niche. This species is an efficient converter of energy.

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