Cicadas are largely harmless to humans and animals, though their exoskeletons can be a stomach irritant to pets that consume them. Although not ordinarily considered a pest, the females may damage young saplings during their egg laying if they are present in high numbers. Similarly, the underground nymphs feed on tree roots, and enormous numbers may harm young or vulnerable trees. However, the sap is taken from roots very slowly over months and years, and most trees survive.