Offspring Defensive Investment Covaries With Brood Value in a Female Cobweb Spider

ABSTRACT

Maternal investment in offspring defense is expected to enhance offspring survival and parental reproductive success. In cobweb spiders that construct detritus‐based, bell‐shaped retreats, these structures serve to protect the spiderling. The brood value hypothesis predicts that such defensive investment should be proportional to brood value (e.g., egg sac mass and number). We tested this hypothesis in the cobweb spider Campanicola campanulata by conducting field measurements of retreat architecture and maternal defensive investment in relation to egg sac presence, weight, and total grains. As predicted, females with egg sacs constructed larger retreats, and investment increased with both egg sac mass and egg count. These results support the brood value hypothesis and highlight retreat architecture as a crucial yet understudied component of parental care in spider.