Parent-offspring communication in response to predators in a subsocial treehopper (Hemiptera : Membracidae : Umbonia crassicornis)

Rb. Cocroft, Parent-offspring communication in response to predators in a subsocial treehopper (Hemiptera : Membracidae : Umbonia crassicornis), ETHOLOGY, 105(7), 1999, pp. 553-568
Citations number
Categorie Soggetti
Animal Sciences","Neurosciences & Behavoir
Journal title
ISSN journal
0179-1613 → ACNP
Year of publication
553 - 568
SICI code
The defense of offspring from predators is an important aspect of maternal care in the treehopper Umbonia crassicornis. Nymphal offspring develop in a dense cluster around a host plant stem; and laboratory studies show that t hey can solicit maternal defense using synchronized vibrational signals. Un derstanding the function of communication: however, requires not only an ex perimental investigation of the responses of receivers, but also a descript ion of the context in which signaling takes place in nature. In this study I asked how offspring and parents signal in response to natural predators i n the field. I filmed parent-offspring groups to record the behavior of U. crassicornis and their wasp predators (Hymenoptera: Vespidae: Pseudopolybia compressa), along with the substrate-borne vibrational signals produced wi thin the group. I compared the signaling behavior of nymphs, and their moth ers, in three contexts: when the family group was undisturbed, when a preda tory wasp was present, and when the predator had departed. I assessed the i mportance of nymphal signals in recruiting the female's initial response by determining whether females or their offspring responded first to a predat or's approach. The nymphs produced few synchronized signals when undisturbe d, but increased their signaling rate 150-fold in the presence of a wasp. T he 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 first approach, females respond ed before the offspring signaled in over half the encounters. Taken togethe r, these results suggest that offspring signals function to influence the m other's behavior throughout a predator encounter, not just to alert her whe n the predator first appears. Defending females produced signals at a low r ate throughout the day and did not significantly increase this rate when a wasp approached. Instead, females began signaling at a high rate only after a wasp had departed. Maternal signals map function to reduce nymphal dispe rsal after predation events, to reduce the costs of vigilance, or to modify nymphal signaling thresholds in the event of a re-encounter. Both offsprin g and their mothers, then, signal in response to predators, but using diffe rent signals and at different stages of a predation event. In conjunction w ith experimental studies of signal function, these results show that commun ication is important in maternal defense of offspring in these subsocial in sects.