Body-size influence on defensive behavior of Amazonian moths: an ecophysiological approach

Abstract

Ectotherm locomotion is restricted by low temperatures, and many species, such as some flying insects, need to achieve thermal thresholds before taking off. Body size influences heat exchange between an animal and the environment. Therefore, larger animals have higher thermal inertia, and necessarily spend more time in pre-flight warming up, a critical period when they remain exposed and more susceptible to predators. Thus, one could expect larger animals, along their evolutionary history, to have developed a more diversified repertoire of defensive behaviors when compared to their smaller counterparts. Moths are an interesting model for testing this hypothesis, as they exhibit considerable variation in body size and many species present pre-flight warming up by muscle shivering, an evidence of thermal restriction on locomotion. I registered the responses of 76 moths immediately after simulating the attack of a predator and then associated behavioral response to body size. I conducted the experiments at 20 and 25 degrees C to check for possible thermal restrictions on behavior, and identified animals to the family level to check for the effects of a common phylogenetic history. When disturbed at 25 degrees C, smaller moths tend to fly, while larger ones tend to run. At 20 degreedC almost all moths ran, including the smaller ones, indicating a possible thermal restriction on flight. Corroborating the proposed hypothesis, a more diversified repertoire of defensive behaviors was registered among larger moths. An alternative interpretation would be that common behaviors among related moths could be explained by common phylogenetic histories. However, two facts support the physiological restriction hypothesis: (1) the analysis within Sphingidae and Geometridae (not closely related families) showed similar results to those of the overall analysis, and (2) a more diverse repertoire of defensive behaviors was associated to the lower, and therefore more restrictive to locomotion, temperature (20 degrees C).

Size dependent predation risk in cryptic and conspicuous insects

“…Furthermore, various thermal constraints, as well as those related to flight physiology may be present in different species (e.g. Oliveira 2005). Additionally, we cannot ignore the phylogenetic constraints on body size, since, typically, closely related species of Lepidoptera appear to show only small differences in body size.…”

A molecular phylogeny for the pyraloid moths (Lepidoptera: Pyraloidea) and its implications for higher‐level classification

“…Ellsworth et al , 1989; Cavalieri & Kocak, 1995; Onstad & Gould, 1998; Small, 2007; Arthur, 2008; Tao et al , 2008a, b; Oppert et al , 2010), behavioral ecology (e.g. Oliveira, 2005; Lewis & Wedell, 2009; Ingleby et al , 2010; Lewis et al , 2011), the genetics and evolution of pheromone communication systems (e.g., Roelofs et al , 2002; Lassance, 2010; Fuji et al , 2011), parasitoid–host co‐evolution (e.g. Eliopoulos & Stathas, 2003; Roberts et al , 2006; Niogret et al , 2009), and physiology and development (e.g.…”

Intraspecific variation in body size of bumblebee workers influences anti‐predator behaviour

“…In fact, previous studies showed that small workers of B. terrestris and B. lapidarius are faster and more agile than larger ones, for example at handling flowers of Cytisus scoparius (Stout, ). Similarly in lepidopterans, larger moths developed a more diverse repertoire of defensive behaviours, owing to physiological constrains of flight, in comparison with small moths (Oliveira, ). In a coleopteran ( Callosobruchus chinensis ), a positive correlation was observed between body size and death‐feigning duration, an alternative and rarer anti‐predator defence strategy (Hozumi & Miyatake, ).…”

“…anti-predator behaviour, artificial spiders, Bombus terrestris, intraspecific variability, nectar availability, pollinator size are often exposed to various flower-dwelling predators (Dukas & Morse, 2003, 2005. In addition, they exhibit a high degree of intraspecific variation in body size (Goulson, 2003).…”

“…Such predictions are proposed to be driven by different mechanisms, being those the low amount of resources stored and invested in the hive for small size bees, and the lower probability of being captured upon attack (i.e., susceptibility) for large size bees (Rodríguez-Gironés & Bosch, 2012). Indeed, patches harbouring flower-dwelling spiders are much visited by large social bees such as bumblebees, but avoided by more vulnerable bees such as honeybees (Dukas & Morse, 2003, 2005Morse, 2007), indicating that, in comparisons across species, larger pollinators are less susceptible to predation risk. However, to our knowledge, the influence of within-species variation in body size on predation risk has not been studied (but see Jones & Dornhaus, 2011), nor has this been examined in the field.…”