Data from Cleaning up after a meal: the consequences of prey disposal for pit-building antlion larvae

Please see the following publication for further details:

Beponis, L. M., R. E. O'Dea, V.-A. Ohl, M. P. Ryan, P. R. Y. Backwell, S. A. Binning, and T. M. Haff. 2014. Cleaning up after a meal: the consequences of prey disposal for pit-building antlion larvae. Ethology:doi:10.1111/eth.12257

We studied pit construction by antlion larvae, Myrmeleon acer, and the behaviour of Argentine ants, Linepithema humile, an important prey of M. acer , at the Australian National University Kioloa Coastal Campus, New South Wales, Australia (latitude 35º32’ S longitude 150º22’ E, 10 m elevation) in April 2013.We measured the diameter of pits constructed by antlion larvae in the wild with callipers. We captured and placed each antlion in a separate, labelled container, and measured their head width using dissecting microscopes fitted with granicules. In total, we obtained pit diameter and head size estimates from 133 wild antlions.

We tested ant response to dead conspecifics around antlion pits using artificial pits. We set up 80 plastic enclosures (9 cm X 12 cm; diameter X height) filled 6 cm high with sand. An “encounter zone” was lightly etched around each pit using a 4 cm diameter cylinder of cardboard.

The experiment consisted of four treatments with 20 replicates of each. Treatment 1: 2-3 day old ant carcasses (‘old carcasses’) were placed around the pits. Treatment 2: < 12 h old ant carcasses (‘fresh carcasses’) were placed around the pits. Treatment 3: ant-sized pieces of Eucalyptus bark (‘bark control’) were placed around the pits. Treatment 4: no objects were around the pits (‘clear pit’). Each treatment replicate had two observers, who were not blind to the treatments. Intra- and inter-observer reliability was high.

For treatments 1-3, we placed three of the objects in an equilateral triangular around the edge of the pit, just within the encounter zone to standardize the chance that live ants would encounter the objects when approaching from any direction. For each replicate, we dropped one live ant at the edge of the round container, and recorded the ant’s behaviour with a stopwatch for 3 min. We recorded: a) the time (s) taken for the ant to first enter the encounter zone; b) the number of times the ant entered the encounter zone; c) the total time (s) the ant spent in the encounter zone; d) the time (s) taken to first fall into the pit; and e) the total number of times each ant fell into the pit. For treatments 1-3 (ants and bark) we also recorded f) the number of interactions the ant had with the objects placed around the pit, defined as the ant directly bumping into or stopping to inspect an object.