ParentÐOffspring Communication in Response to Predators in a Subsocial Treehopper "Hemiptera] Membracidae] Umbonia crassicornis#

The defense of o}spring from predators is an important aspect of maternal care in the treehopper Umbonia crassicornis[ Nymphal o}spring develop in a dense cluster around a host plant stem\ and laboratory studies show that they can solicit maternal defense using synchronized vibrational signals[ Understanding the function of communication\ however\ requires not only an experimental inves! tigation of the responses of receivers\ but also a description of the context in which signaling takes place in nature[ In this study I asked how o}spring and parents signal in response to natural predators in the _eld[ I _lmed parentÐo}spring groups to record the behavior of U[ crassicornis and their wasp predators "Hymenoptera] Vespidae] Pseudopolybia compressa#\ along with the substrate!borne vibrational signals produced within the group[ I compared the signaling behavior of nymphs\ and their mothers\ in three contexts] when the family group was undisturbed\ when a predatory wasp was present\ and when the predator had departed[ I assessed the importance of nymphal signals in recruiting the female|s initial response by determining whether females or their o}spring responded _rst to a predator|s approach[ The nymphs produced few synchronized signals when undisturbed\ but increased their signaling rate 049!fold in the presence of a wasp[ The nymphs continued to signal as long as the wasp was present\ and in some cases after it had left\ especially if the wasp had contacted or removed a nymph during the encounter[ During a wasp|s _rst approach\ females responded before the o}spring signaled in over half the encounters[ Taken together\ these results suggest that o}spring signals function to in~uence the mother|s behavior throughout a predator encounter\ not just to alert her when the predator _rst appears[ Defending females produced signals at a low rate throughout the day and did not signi_cantly increase this rate when a wasp approached[ Instead\ females began signaling at a high rate only after a wasp had departed[ Maternal signals may function to reduce nymphal dispersal after predation events\ to reduce the costs of vigilance\ or to modify nymphal signaling thresholds in the event of a re!encounter[ Both o}spring and their U[ S[ Copyright Clearance Center Code Statement] 9068!0502:88:0946Ð9442,03[99:9