Visually-guided defensive behaviors in triatomines (Heteroptera: Reduviidae)

Reduviidae is a family of insects mainly composed of predatory species known as assassin bugs and obligate blood-feeding species known as kissing bugs. Although both groups possess relatively well-developed compound eyes, image vision has only been associated with feeding behaviors in assassin bugs. Here, we studied whether vision plays a role in supporting defensive behaviors in kissing bugs. Our findings reveal that Rhodnius prolixus consistently responds to visual looming stimuli by either freezing or escaping and that it can rapidly switch between these behaviors based on the ongoing stimulus information. By exposing animals to stimuli with different dynamics, we observed that escape responses were primarily evoked by stimuli mimicking the approach of a predator at a sustained velocity. Altering the contrast of the stimuli showed that freezing occurred regardless of the contrast, whereas escape was elicited only by high-contrast stimuli. Additionally, presenting numerous stimulation trials with short intertrial intervals yielded no habituation of the responses. Our results demonstrate a clear role of the visual system in supporting defensive behaviors in kissing bugs. These responses can be evoked in a fast and flexible manner according to the ongoing information provided by the stimulus. Similar to what has been observed in highly visual arthropods, we found that the probability of occurrence and intensity of the evoked defensive responses depend on the evaluation of the impending risk that the visual stimuli entail.