 At the mechanical level, both genetic factors (e.g., smaller adult body size) and environmental influences (e.g., higher provisioning levels) may play a role.In a different aspect, the selection pressure exerted by the European social parasites such as "Polistes sulcifer" and "Polistes semenowi" might have caused the developmental times in "P. dominula" to be shorter.Because these parasites normally attack the host nests just prior to worker emergence, it would be advantageous for "P. dominula" to have a shortened brood developmental time.