The use of floral hunting sites by a generalist sit-and-wait predator: Site choice, prey capture, and the importance of nectar-feeding by the ambush bug Phymata pennsylvanica (Heteroptera: Phymatidae)

Flowers might be expected to be important resource patches for generalist predatory arthropods, due to the high abundance at these sites of nectar- and pollen-feeding insects that could potentially serve as prey. Ambush bugs (Heteroptera: Phymatidae) are generalist sit-and-wait predators that have long been known to be associated with flowers in North American old-field habitats. In addition to hunting on flowers, however, ambush bugs are also found foraging on non-flowering plants. My goal in this dissertation was therefore to understand the ecological factors promoting the use of flowering versus non-flowering hunting sites by the ambush bug Phymata pennsylvanica in an upstate New York old-field.; First, I quantified the ambush bugs' site-occupancy patterns in the field, and found that the bugs showed a relative preference for hunting on flowers. In absolute terms, however, a large proportion of the population was still found on non-flowering plants, due to the much higher abundance of non-flowering relative to flowering sites. Next, I examined the ambush bugs' prey capture patterns in the field, and found that there was little difference between the two site types in terms of prey capture rates and prey consumption rates, although prey were significantly larger on flowers. Lastly, I examined ambush bug nectar-feeding. In laboratory experiments, I found that the consumption of simulated nectar increased ambush bug survival in the absence of prey, but had no benefit when prey were provided at regular intervals at levels typical of the field. Nevertheless, a simple model based on observed prey capture patterns suggested that nectar-feeding could prevent starvation during periods of effectively zero prey availability that result from stochastic variation in the wait-times between successive prey captures. The ambush bugs' preference for flowers can thus be explained by the availability of nectar as a supplementary food source on these sites, as well as possibly the availability of larger prey, while the bugs' continued use of non-flowering sites can be explained by the ephemerality and relative rarity of flowers compared to non-flowering sites, and the relatively small difference in prey capture success for bugs on the two site types.