3D reconstruction of the hissing organ of Grompadorhina portentosa (Blattodea: Blaberidae)

Many insects rely on acoustic signals to communicate. Most Insect species communicate via stridulation, rubbing modified cuticular surfaces to each other and producing friction-based acoustic signals. Very few insects, however, can communicate via voice boxes, modified portions of their respiratory system, similar to most vertebrates. Hissing cockroaches, or simply “hissers,” consists of 20 species distributed across 6 described Genera. They utilize the modified fourth abdominal spiracle, to create their signature hiss. Only one study has been performed on the morphology of the hissing organ in 1979. Our research aims to investigate the structure and function of the hissing organ using cutting-edge imaging technologies, such as MicroCT and Confocal Laser Scanning Microscopy. The distal portion of the spiracle, the atrium, is widened and horn-shaped and is connected to that of subsequent spiracles presumably amplifying the resonance and volume of the hiss. The spiracle does not function as a breathing organ and opens only when the specimen is hissing. It is covered by a sclerotized flap with a resilin-rich margin, called the reed, which resonates when air is pushed out from the trachea. Although hissing has been reported only in the last larval stages and adults, we found modified spiracles in earlier instars, indicating that voice box-based sound production might develop in younger specimens. The functioning of the hissing organ is modeled using physical models generated via 3D printers.