Learning in insects has been well documented, particularly for adult holometabolous insects. Less is known about learning in larval and nymphal insects or hemimetabolous insects. Previous studies of the Chinese praying mantis (Tenodera sinensis), a hemimetabolous predator, have demonstrated that sixth instar nymphs can learn to avoid eating toxic milkweed bugs (Oncopeltus fasciatus) after sampling the noxious prey. However, another study that used third instar nymphs showed that mantises still eat the toxic prey despite previous sampling. Taken together, these studies highlight the need to examine the ontogeny of learning. Is learning in mantids an age- or stage-dependent behavior? Once an individual has learned, how long does the memory persist, and is memory retention age- or stage-dependent? Does memory persist across a molt? To examine these questions, we will present mantises at each nymphal instar with toxic milkweed bugs, and assess their learning. If the mantis learns to avoid the prey, retention of this learned response will be tested every other day until the mantis ‘forgets’ and attacks the prey. Control mantises will be presented with non-toxic milkweed bugs fed on sunflower seeds. To our knowledge, no previous study has followed the ontogeny of learning from first nymph to the adult.