Ambush bugs, Phymata pennsylvanica Handlirsch (Heteroptera: Phymatidae), are generalist sit-and-wait predators commonly found hunting on old-field flowers in the Northeastern United States. Individuals will often probe flowers for long periods, suggesting that the bugs are feeding on nectar. The objective of the reported studies was to examine the ambush bug’s ability to detect and use simulated and real nectar as food. In a field experiment, ambush bugs that were restricted without prey on inflorescences survived longer than bugs restricted to nonflowering sites, thus indicating that the bugs were able to gain nutritive material directly from flowers. In laboratory choice tests, individuals were more likely to drink from a dilute sucrose-solution than from a plain water solution, indicating that the bugs were able to identify nectar as a food resource. Last, individuals provided with sucrose-solution in laboratory feeding trials survived significantly longer in the absence of prey than individuals given only plain water or nothing and also lost mass at a slower rate. However, juveniles could not molt past any instar in which they had fed on only sucrose solution. As with many other generalist predatory arthropods, then, plant-feeding in nature likely allows ambush bugs to survive longer when prey are scarce, but plant food alone is likely to be nutritionally insufficient for normal growth and development. Further research to examine patterns of prey scarcity and possible trade-offs between the consumption of nectar and the consumption of prey will help to clarify the overall role of nectar-feeding in ambush bug ecology.