 Completely developed adult fleas can live for several months without eating, so long as they do not emerge from their puparia.Optimum temperatures for the flea's life cycle are 21 °C to 30 °C (70 °F to 85 °F) and optimum humidity is 70%.Adult female rabbit fleas, "Spilopsyllus cuniculi", can detect the changing levels of cortisol and corticosterone hormones in the rabbit's blood that indicate it is getting close to giving birth.