Encounters between adult spined assassin bugs,Sinea diadema (F.) (Hemiptera: Reduviidae): The occurrence and consequences of stridulation

Abstract

The sequence of events leading to the resolution of agonistic interactions between adult femaleSinea diadema (F.) (Hemiptera: Reduviidae) is described. Contact between these predatory bugs resulted in a series of defensive and offensive actions, including stereotypical posturing and striking movements of the forelegs. Although these encounters usually escalated in intensity and frequency of contact, they rarely resulted in injury or cannibalism. Instead, one individual retreated from the perch. The original resident on the perch retreated in 70% of the encounters. Stridulation was observed during 33% of the encounters. Stridulating individuals retreated more often than their nonstridulating opponents, indicating that stridulation may be a startle mechanism employed by temporarily disadvantaged individuals to escape from encounters. These encounters were conflicts in which the participants are both potential predators and possible prey. The combinations of posturing, striking, and stridulation that occurred during encounters may have provided each bug with information concerning the identity and relative fitness of its opponent. If an individual is fit, it may be advantageous for it to probe the defensive capabilities of its opponent, since its own risk is low, and a less fit opponent could be killed and eaten.