On the face of it, the phone reports didn’t seem too odd because boxelder bugs use their piercing/sucking mouthparts to penetrate plant seeds to extract food. They feed on a wide range of plant seeds beyond the samaras of their namesake host and goldenrain trees were beginning to produce seed when I started getting the bug reports.
However, a phone call from Steve and a follow-up visit revealed that we weren’t dealing with boxelder bugs; we were dealing with Goldenrain tree bugs. The mulch beneath several goldenrain trees at the zoo were "crawling" with the bugs.
This was unexpected because the bugs are native to the southeastern U.S. where they evolved to feed on various native members of Sapindaceae such as the Florida soapberry (Sapindus saponaria). The native hosts accounts for their common name of “soapberry bug.” They are also called “redshouldered bugs” with this descriptive common name referring to the red edges of the pronotum (the thoracic segment behind the head).