Earthworms have a major role in soils and are used as biological indicators for ecological risk assessment. Aporrectodea caliginosa s.s. is one of the dominant earthworm species in agroecosystems and a good candidate for ecotoxicological testing. In order to improve knowledge on its life cycle, we performed growth and reproduction experiments. These data were used to calibrate an energy-based model that displayed good descriptions of A. caliginosa life cycle parameters under different feeding conditions (ad libitum, food limitations, or absence of food). Here we showed that the maintenance costs were negligible, resulting in a linear growth in length when food was provided ad libitum (i.e., without any restriction). We also found that the switch from the juvenile to adult stage depended on the individual weight, and that the threshold weight was not influenced by the amount of provided food (horse dung). Moreover, we provided evidence that once adults, if they were not isolated from other individuals, the energy was entirely allocated to cocoon production, which only depended on the available food amount, without any effect of the earthworm density. Finally, we discussed the usefulness of our energy-based model to support the set up and analyses of ecotoxicological tests and experiments.