Diel shifts in treehopper-tending by ants and wasps in Costa Rica (Hymenoptera)

We examined the activity pattern of seven ant species (Hymenoptera: Formici dae; Brachymyrmex sp., Camponotus atriceps, Camponotus integellus, Camponot us sp., Crematogaster nigropilosa, Pheidole biconstricta, and Pheidole sp.) and one wasp species (Hymenoptera: Vespidae; Parachartergus apicalis) tend ing two treehopper species (Homoptera: Membracidae; Antianthes sp, and Cero sa sp.) on Acnistus arborescens trees (Solanales: Solanaceae) at San Luis B iological Station in Costa Rica. We observed hymenopteran attendants at 61 of 67 treehopper aggregations. All eight hymenopteran species tended tree-h oppers during the day, but only three of the ant species (C. atriceps, C. n igropilosa, and P. biconstricta) also tended at night. Whereas 23 treehoppe r aggregations had the same species of ant tending during both day and nigh t, 19 aggregations had two different attendant species, one diurnal and one nocturnal. In all 19 cases, the nocturnal tender was Camponotus atriceps, a large carpenter ant. Several earlier studies have reported a diel shift i n species tending homopterans. In all cases, the nocturnal tender was a spe cies of Camponotus. A possible cause for this diel shift relates to the rel atively large body size of Camponotus workers, which may allow them to disp lace smaller ants at night, but may be a disadvantage during the day becaus e it makes Camponotus workers a preferred target for diurnal parasites and predators.