Norden and Krombein's 1993 search for the wasp took place in the rain forest of Gilimale, near the Sinharaja Forest Reserve where Rickson had first found the wasp. They discovered that the wasp was, indeed, rare and were only able to collect nine more specimens. Both researchers were, however, able to collect thousands of internodes of the Humboldtia laurifolia , in which the wasps nest, before returning to Washington, D.C. Unopened stems were placed directly into alcohol for subsequent study back in the Department of Entomology's lab, where they were carefully cut open and the contents examined. Krombein arranged separate funding to accompany Norden back into the field. On this trip, Norden and Krombein were most interested in examining the association of insects and other invertebrates that lived within the stems of the Humboldtia laurifolia .
Internodes are usually narrow at the base and enlarged at the top where a natural opening develops.
Inside the stem, the central pith breaks down as the stem ages, collapsing against the inner wall and creating a hollow region. Certain ants, wasps and bees apparently gnaw at and enlarge the slitlike openings, then clean out the pith inside, creating a hollow cavity in which to nest and lay their eggs. A total of 15 different ant species, as well as a variety of bees, wasps, beetles, spiders and even an arborial earthworm, nest in the internodes. A lengthy treatise on Norden and Krombein's research on this plant is soon to be published by Smithsonian Institution Press as part of the Smithsonian Contributions to Zoology series. Traces of this pollen were later found in the Krombeinictus' nests when they were viewed under the museum's scanning electron microscope.