Effect of substrate temperature on behavioural plasticity in antlion larvae

Abstract

Temperature is of crucial importance, affecting all aspects of insect life such as survival, development and daily activity patterns, and consequently behaviour. In the present study we evaluated the effect of temperature on the behavioural plasticity of antlion larvae, the sit-and-wait predators, which are considerably more dependent on local habitat conditions. We provided ethological descriptions of pit construction and feeding behaviour. An increase in temperature led to greater activity and consequently to greater frequency of sand tossing during pit construction. Larvae constructed bigger pits at higher temperatures, but required less time than at lower temperatures, when the resulting pits were the smallest. At low temperature, larvae required more time for feeding, and behaviour followed a core pattern with little variety, in comparison to behaviour at high temperatures. Two behavioural patterns occurred only at the highest temperature: ‘relocation’ and ‘submergence’, presumably in response to high temperatures.

Thermal dependence of trap building in predatory antlion larvae (Neuroptera: Myrmeleontidae)

“…The results of our experiment show that higher soil temperatures resulted in more frequent trap building and traps with a larger diameter and volume. These findings are consistent with those from some earlier studies on trap building in antlion larvae (Kitching 1984 ; Arnett and Gotelli 2001 ; Klokočovnik et al 2016 ), but they contrast with the conclusions of other studies showing either no clear effects of temperature on trap volume (Rotkopf et al 2012 ) or negative effects of temperature on trap-building frequency (Klein 1982 ). Our findings do not support hypothesis 2, which predicts that antlion larvae challenged by cooler conditions might compensate for their reduced behavioral capacity to immobilize prey and prevent rescue by ant nest-mates by maintaining larger traps.…”

“…Given that the capacity to build traps can directly reflect the dependence of larval behavior and metabolism on temperature, we expected soil temperature to positively affect pitfall trap volume (hypothesis 1). Such an effect was previously found in Myrmeleon pictifrons (Kitching 1984 ), Myrmeleon immaculatus (Arnett and Gotelli 2001 ) and E. nostras (Klokočovnik et al 2016 ). However, other studies showed contrasting effects of temperature on trap building.…”

“…Furthermore, the pressure of antlions on different-sized invertebrates also seems to change independently of larval size, increasing either in warmer microhabitats or during the warmer parts of a season. Indeed, Klokočovnik et al ( 2016 ) showed that the capture and consumption of prey by antlion larvae were faster at higher temperatures. Given that antlion larvae can rapidly re-establish their traps, even a brief change in environmental temperatures occurring over days or weeks may significantly alter the pressure of antlion larvae on prey of different sizes.…”

“…As antlion larvae live at the mercy of local conditions necessary for effective hunting (dry, sandy areas), they should experience selection for increased thermal tolerance and the capacity to perform over a wide range of temperatures. Unfortunately, thermal dependence of hunting behaviors has been studied in only a limited number of antlion species, such as Myrmeleon immaculatus and Euroleon nostras , which seem to actively prefer shaded areas (Haub 1942 ; Green 1955 ; Klein 1982 ; Heinrich and Heinrich 1984 ; Arnett and Gotelli 2001 ; Klokočovnik et al 2016 ). Such shade-preferring species may not have as high thermal tolerance as those that do not avoid open areas and occur in fully sun-exposed locations.…”

Prey detection in antlions: propagation of vibrational signals deep into the sand

“…The activity of antlion larvae is highly temperature‐dependent (Klein, ; Marsh, ; Ábrahám, ; Scharf & Ovadia, ; Klokočovnik et al, ; Antoł et al, ); therefore, antlions migrate deep into the sand at high sand‐surface temperatures (Heinrich & Heinrich, ; Matsura, ; Van Zyl et al, ). Antlions are extremely sensitive to substrate vibrations produced by prey moving on the sand surface (Devetak et al, ; Fertin & Casas, ; Devetak, ; Martinez et al, ); therefore, we anticipate that vibrational cues would stimulate them to move to the surface when buried in deeper layers of sand.…”