Abstract
Robust body armor is one of many anti-predator strategies used among animal taxa. The exoskeleton of insects can serve as the secondary defense mechanism in combination with the primary defense such as warning color. Aposematic Pachyrhynchus weevils advertise their unprofitability and use their robust exoskeleton for effective defense against lizard predators. While the mature weevils survive after the predatory attack, the soft teneral ones can easily be consumed. To reveal how the mature weevils achieve such effective protection, we investigated the ontogenetic changes in the microstructure and material properties of the exoskeleton of the adult weevils. We also tested the functional role of a weevil-specific structure, the fibrous ridge, in the robustness of the elytral cuticle of the mature weevils. The results showed that the mature weevils have thicker, stiffer and more sclerotized cuticle than the teneral ones. The fibrous ridges in the endocuticle considerably increase the overall stiffness of their cuticle. Together these biomechanical strategies enable Pachyrhynchus weevils to achieve robust body armor that efficiently protects them from lizard predation.
Highlights
Well-defended aposematic prey animals advertise their unprofitability to potential predators by visual, acoustic or olfactory cues (Poulton, 1890; Ruxton et al, 2004)
The stiffness of the lizard tooth was significantly higher than both the mature (t = 7.823, p < 0.001) and teneral cuticle (t = 9.454, p < 0.001). Both mature and teneral Pachyrhynchus weevils advertise aposematic coloration as primary defense against predation. When they encounter naïve lizard predators, the teneral weevils are consumed, while the mature weevils survive the attack without damage (Wang et al, 2018)
The “secret weapon” of the mature weevils hides in their colorful exoskeleton
Summary
Well-defended aposematic prey animals advertise their unprofitability to potential predators by visual, acoustic or olfactory cues (Poulton, 1890; Ruxton et al, 2004). These cues often function as reliable warning signals through the linkage between the conspicuousness and an effective secondary defense. Prey animals use mechanical protections, for example, spines or hard armor, to render themselves unpalatable (Ruxton et al, 2004; Stevens, 2013)
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