 Within a few hours, the daughter checks whether it will be worth the effort. Through lab studies, scientists have asked the daughter what it's looking for. The clear answer is the amount of nutritional energy that it is likely to be able to extract from that particular host, based on its overall health and the concentration of nutrients circulating through its body. In one experiment, daughters grown among hawthorn plants chose the hawthorns that had been grown with extra nutrient supplements and rejected the ones that had been grown in a nutrient-scarce environment.