Habitat choice and complex decision making in a trap-building predator

The choice of suitable habitats may maximize the survival and reproduction of the individuals choosing them. We examined habitat choice by wormlions, small sand-dwelling insects that construct pit-traps to capture prey. Wormlions prefer shaded habitats over lit ones, do not relocate away, and construct large pits there. However, they compromise over this preference if the shaded habitat is interfered with unfavorable conditions, shallow sand, surface obstacles, or high wormlion density, which hinder them from constructing large pits.The selection of a suitable habitat may maximize the survival and reproduction chances of individuals. We examined the habitat choice of wormlions, small sand-dwelling insects that construct pit-traps to capture prey. Unlike the well-studied antlions, which employ a similar hunting strategy, wormlion behavior has not been thoroughly studied. We first determined whether wormlions prefer 1) shaded versus lit, 2) deep versus shallow sand, and 3) surface-obstructed versus clear microhabitats. The first option of each of the three pairs was highly preferred. In unfavorable microhabitats, larvae were also less likely to construct a pit, mainly in shallow sand, and moved over longer distances. Next, we sought to determine whether the choice is additive (taking more than a single factor into account), hierarchical (ranking the factors according to an order of preference), or based on a threshold rule (accepting a microhabitat that crosses a quality threshold). Combining shade with one of 3 environmental factors - surface obstacles, shallow sand, or high conspecific density - led to lower proportions of wormlions choosing shade. In other words, a combination of shade and any factor was no longer preferred over lit and otherwise favorable microhabitats. We thus conclude that the wormlions' microhabitat choice is additive, taking more than a single factor into account, and that favorable conditions of any sort are traded-off against one another.