Antlion Foraging: Tracking Prey Across Space and Time

Abstract

To capture their prey, larval antlions invest energy in building and maintaining conical pit traps in fine‐particulate substrate. The resident antlions (Myrmeleon immaculatus) at Sleeping Bear Dunes National Lakeshore, Michigan, USA, seldom relocated their pits, and we wondered whether this site fidelity could be understood as an optimal (or near‐optimal) response to observed spatial and temporal variation in prey availability. To determine this, we considered a large number of compound foraging strategies, each composed of the number of days over which the antlion evaluates foraging success at a site; the weighted‐average foraging success during this interval, below which threshold the antlion moves to a new site; and the length of the random walk taken by the antlion to a new pit location. Using Monte Carlo simulation, we determined the expected net energy gain from each of these strategies by antlions rewarded according to the field data set. The overall highest gain strategy generally agreed with our a priori expectations for the observed pattern of patchiness in prey availability over space and time. Moreover, the corresponding optimal frequency of pit relocation, 1.65 moves over the observation period of ∼8 wk, is in rough agreement with field observations. However, the gain surface was relatively flat: 60% of the investigated strategies yielded within 8% of the maximum gain. When costs of pit relocation were reduced, maximal gain strategies shifted to generate frequent movement, suggesting that the magnitude of such sampling costs may control the foraging strategy in environments with high spatiotemporal variability.

Direct and indirect effects of soil structure on the density of an antlion larva in a tropical dry forest

“…Finally, the behaviour of adult antlions may affect larvae density if they often oviposit in fine-grained soils ( Lucas, 1989 ). However, larvae are very mobile and often travel distances of several metres to relocate their pits ( Heinrich & Heinrich, 1982;Crowley & Linton, 1999;Farji-Brener, 2003 ). Therefore, female oviposition behaviour may contribute to the origin of larvae density but not to its maintenance ( Gotelli, 1993 ).…”

“…Antlion larvae (Neuroptera: Myrmeliontidae), the focus of the present study, are sit-and-wait predators that dig conical pits in loose soil to capture small arthropods (usually ants) that fall into the pit. Both abiotic and biotic factors may affect the fitness of such organisms, and therefore patterns of variation in their local abundance ( Gotelli, 1993;Crowley & Linton, 1999 ). However, several studies suggest that abiotic factors are relatively more important than biotic factors ( Scharf & Ovadia, 2006 ).…”

“…However, several studies suggest that abiotic factors are relatively more important than biotic factors ( Scharf & Ovadia, 2006 ). For example, while local abundance of antlion pits is not correlated with prey availability ( Gotelli, 1993( Gotelli, , 1996( Gotelli, , 1997Crowley & Linton, 1999 ), abiotic factors such as soil moisture, leaf litter, soil temperature, rainfall, and soil structure often restrict the habitat available to antlions ( McClure, 1976;Simberloff et al , 1978;Boake et al , 1984;Marsh, 1987;Lucas, 1989;Gotelli, 1993;Gatti & Farji-Brener, 2002;FarjiBrener, 2003 ).…”

“…Antlions prefer soils with a high proportion of fine-grained particles, for several reasons: the larvae require less time to build the pit, and construct larger and deeper pits that increase prey capture ( Lucas, 1985;Botz et al , 2003;Farji-Brener, 2003;Devetak et al , 2005 ). Consequently, antlions are often less abundant in areas with high soil surface temperature, soils exposed to rainfall, sites with high abundance of leaf-litter, and coarse-grained soils ( McClure, 1976;Lucas, 1982;Gotelli, 1993;Crowley & Linton, 1999;Arnett & Gotelli, 2001;Lomascolo & FarjiBrener, 2001;Farji-Brener, 2003 ).…”

Cleaning Up After a Meal: The Consequences of Prey Disposal for Pit‐Building Antlion Larvae

“…). Trap relocation offers one solution to this potential dilemma, but building traps requires a significant energy investment (Lucas ; but see Elimelech & Pinshow for a counter‐example), and evidence suggests that relocation is rare (Matsura ; Crowley & Linton ; Scharf & Ovadia ; Hollis et al. ).…”