Chemical defense of giant springtail Tetrodontophora bielanensis (Waga) (Insecta: Collembola)

The giant springtail, Tetrodontophora bielanensis (Waga), is characterized by integumental openings (pseudocells) from which small droplets of a sticky defensive fluid are secreted after molestation. The secretion originates initially from secretory cells below the pseudocellae; subsequent irritations result in release of hemolymph, which was identified by both chemical and microscopical methods as well as by scanning electron microscopy. Bioassays with topically treated ground beetles Nebria brevicollis showed that the pseudocellular quid evokes a total disorientation and cleansing behavior of the beetle. The main constituents were identified as the following pyrido-pyrazines: 2.3-dimethoxpyrido[2.3-b]pyrazine (1), 3-isopropyl-2-methoxy pyrido[2,3-b] pyrazine (2), and 2-methoxy-4H-pyrido[2,3-b]pyrazine-3-one (3). These alkaloids are mainly present in the pseudocellar quids of female and male springtails but are absent in their food or feces. Minor amounts are found in the hemolymph of adults, while larvae contain traces of 2 only. All compounds were synthesized and tested for activity. In natural concentrations, the synthetic alkaloids elicited the same effects from the ground beetles as the pseudocellar fluid.