Body size increases greatly during ontogeny in most animals and is often accompanied by dramatic shifts in foraging strategies and hence food resources. Orb-weaver spiders provide an interesting case, where a relatively homogeneous foraging strategy, aerial silk webs, is employed across all ontogenetic stages. Orb webs are spun soon after spiders emerge from the egg sac through growth of up to two orders of magnitude in body size. The sizes of prey targeted by the spiders are also likely to increase as spiders develop. Here, we examine how relative silk investment, web architecture, and the material properties of silk in webs change during ontogeny in the orb-weaver Neoscona arabesca. We also quantify two emergent properties of web performance – prey stopping potential and stickiness. We find that silk investment increases isometrically with body size, with the exception of greater than expected glue production in larger spiders. Larger spiders spin larger webs, with smaller radii, but the increased volume of all silk types and greater toughness of the capture spiral silk result in the isometric scaling of stopping potential. The strength and toughness of sticky capture spiral thread increases with diameter and hence also with ontogeny, a size scaling pattern that mirrors an evolutionary pattern across spider species. Dragline thread material properties do not change over ontogeny. The improved material properties of capture spiral threads and the increased absolute stopping potential of webs are consistent with the hypothesis that rare, large prey items play a crucial role in spiders reaching adulthood and in maximizing fecundity of female orb-weaver spiders.
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