The origin of aggregate silk glands and their production of wet adhesive silks is considered a key innovation of the Araneoidea, a superfamily of spiders that build orb-webs and cobwebs. Aggregate glues are humidity responsive biomaterials, but responsiveness varies considerably among araneoid spiders. Despite a growing interest in the biomechanics of aggregate glues, very little is known about their constituent proteins. Here we describe the material behavior and quantitative proteomics of the aggregate glues of two cobweb weaving species, the Western black widow, Latrodectus hesperus, and the common house spider, Parasteatoda tepidariorum. We identified 47 and 33 aggregate glue proteins for the two species, respectively. These proteins were highly enriched for glycosylation and phosphorylation relative to proteins found in silk fibers, which likely explains aggregate glue stickiness. Black widow aggregate glue droplets were found to be more extensible, and thus tougher, than house spider aggregate glue droplets, although these differences were not significant. The toughness of both species’ droplets exceeded those of most orb-web weaving species that have been characterized. House spider droplets were more responsive to humidity changes than black widow droplets. Differences in humidity responsiveness could be explained by the differences in protein sequence, post-translational modifications, or the non-protein components of the glue droplets. The similar material properties may reflect the conserved protein composition of the two species. Future comparisons will determine if differences in material properties between orb-web and cob-web glue mechanics can be explained by differences in their constituent proteins.