Results of field investigations on web architecture and behavioral investment in different type of female Campanicola campanulata

Maternal investment in offspring defense is a primary determinant of spiderling survival and parental reproductive success. In cobweb spiders that construct detritus-based, bell-shaped retreats, these structures enhance offspring protection. The reproductive value hypothesis predicts that investment in offspring defense is proportional to the potential reproductive value of the brood (e.g., egg sac mass and egg number). We tested this hypothesis in Campanicola campanulata, a species in which females invest heavily in retreat construction that primarily benefits their offspring. Through field investigations, we quantified retreat parameters and maternal investment in relation to egg sac presence, mass, and egg number. As predicted, females with egg sacs built larger retreats, and investment increased with both egg sac mass and egg count. Our results demonstrate that retreat construction in female cobweb spiders is modulated by potential reproductive value. This highlights retreat architecture as a crucial, yet understudied, component of spider parental care, shaped by reproductive benefits.