174 -- Does Male Display Behavior in an Ant-Mimicking Spider Depend on Context and Affect Female Response?

Myrmarachne formicaria is a species of ant-mimicking jumping spider native to Eurasia that was first noticed in the United States in 2001. These spiders get their name from their ant-like body forms and movement of their two forelegs to appear like antennae. They are also sexually dimorphic, with the males having enlarged chelicerae (jaws) that extend out from the front of their face. Males that encounter each other engage in displays that include faceoffs (facing one another and pacing back and forth), putting their abdomens to the side, opening their chelicerae, and even attacking/jabbing at one another. These male displays are usually initiated as a territorial defense mechanism or as they compete for a possible mate. Our experiment was designed to determine whether the intensity and frequency of the male-male behavioral displays were affected by the presence of a female and whether the female showed evidence of a preference for either male. We ran 13 trials in a circular arena divided into three compartments and recorded the interactions of the males before and after adding the female. Each pair of males differed in size by 1 mm or less. Videos were analyzed to quantify the behaviors observed in each trial and compare displays in the absence and presence of females. Female behaviors were also interpreted to see if they showed a preference for the male that prevailed during the trial. The results help us to see how context influences the nature and outcome of male display behavior.