While I was visiting the glades near Calico Rock, Arkansas this past June, I went into town to look along the White River. With the amount of sandstone bedrock in the area, I thought there I might find sandy loam deposits along the river of the type preferred by Cylindera cursitans (ant-like tiger beetle). While I didn’t find any of the beetles, I did see this robber fly (managing only this single shot before it flew off), which I take to be the male of Triorla interrupta based on the pattern of abdominal coloration (the first two segments partially black, followed by two almost wholly black segments). According to BugGuide, this is the only North American species of the genus (a second occurring from Panama to Argentina), and Herschel Raney considers it to be the most common robber fly in Arkansas.
Copyright © Ted C. MacRae 2011