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

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.