Mercury (Hg), in its toxic methylated form (MeHg), is a potent neurotoxin that impairs waterbodies at a global scale due to its broad distribution through atmospheric deposition, and ultimately bioaccumulates in aquatic and terrestrial food webs. Although Hg contamination of aquatic habitats is widespread, MeHg contamination in food webs varies widely across the landscape. One efficient and inexpensive way to monitor Hg contamination in food webs is to use sentinel organisms: taxa that accumulate contaminants in their tissues without significant adverse effects and the concentration in the tissues of sentinels can be used to monitor the amount of a contaminant that is biologically available. Like fish and dragonfly larvae (Insecta: Anisoptera), riparian spiders (Araneae) are often used as sentinels of Hg contamination, particularly to estimate potential Hg exposure to riparian terrestrial wildlife. However, no studies have established a correspondence between spider Hg concentrations and aquatic-dependent biosentinels. The present study addresses this data gap by assessing the relationship between total Hg (THg) concentrations in riparian spiders and dragonfly larvae, another well-established Hg sentinel, collected from 16 sites with a range of Hg impairment. We also assessed whether there were differences in the relationships between spider and dragonfly Hg concentrations due to spider sex. Preliminary results indicate that site mean THg concentrations of long-jawed orb-weaver spiders (Tetragnathidae: Tetragnatha sp.) and dragonfly nymphs were positively correlated (p < 0.001; R² = 0.83, slope = 0.68), indicating that long-jawed orb-weaver spiders can have Hg concentrations that are reflective of Hg impairment in associated aquatic habitats. Spider sex did not have a significant additive effect on Hg concentrations (p = 0.25), and there was no significant difference in the slopes of the two sexes, (p = 59). Our results suggest that long-jawed orb-weaver spider Hg concentrations can reflect the relative Hg levels in other sentinels (dragonfly nymphs), and that both male and female spiders could be used to monitor Hg contamination levels of waterbodies.