Evidence for competition and cannibalism in wormlions

Abstract

Trap-building predators, such as web-building spiders and pit-building antlions, construct traps to capture their prey. These predators compete over sites that either enable the construction of suitable traps, are prey rich, or simply satisfy their abiotic requirements. We examined the effect of intraspecific competition over suitable space in pit-building wormlions. As expected, the ability of wormlions to select their favorable microhabitats—shaded or deep sand over lit or shallow sand—decreased with increasing density. Favorable microhabitats were populated more frequently by large than by small individuals and the density of individuals in the favorable microhabitat decreased with their increase in body mass. The advantage of large individuals in populating favorable microhabitats is nevertheless not absolute: both size categories constructed smaller pits when competing over a limited space compared to those constructed in isolation. The outcome of competition also depends on the type of habitat: deep sand is more important for large wormlions than small ones, while shade is similarly important for both size classes. Finally, in contrast to previous reports, cannibalism is shown here to be possible in wormlions. Its prevalence however is much lower compared to that documented in other trap-building predators. Our findings show that the advantage of large individuals over small ones should not be taken for granted, as it can depend on the environmental context. We present suggestions for the relative lack of competitive advantage of large wormlion individuals compared to other trap-building predators, which may stem from the absence of obvious weaponry, such as sharp mandibles.

Behavioral differences between pit‐building antlions and wormlions suggest limits to convergent evolution

“…2018; Samocha & Scharf 2020; Scharf et al . 2018, 2020, 2021). Of note, as in the case of Anolis lizards, there is no use in looking for morphological similarities between antlions and wormlions.…”

Wind impairs pit trap construction and hunting success in a pit‐building predator

“…Relocation should also depend on the risk associated with movement, such as predation or cannibalism, and the pit construction costs. Wormlions are less cannibalistic than antlions, but cannibalism is still possible (Scharf, Reshef et al., 2021). Pit construction costs are yet unknown in the studied species but are estimated in antlions to be between twice to 10 times that of resting metabolic rate (Elimelech & Pinshow, 2008; Lucas, 1985).…”

Urban Pit-Building Insects Are Attracted to Walls for Multiple Reasons

“…Wormlions reach higher densities than the ecologically similar pit-building antlions [38], possibly owing to much lower rates of cannibalism. That said, competition over suitable sites is evident, with large wormlions being superior over small ones [54]. We chose seven sites at Tel Aviv University, Tel Aviv, Israel (Figure 1; Figure S1 in the Supplementary Material), which we refer to according to the names of the adjacent university buildings: Britannia, Buchmann-Mehta, Central library, Gilman, Green, Mexico, and Schreiber.…”