By peering into the bodies of American cockroaches, researchers have found that a parasitic larva disinfects its host with antibacterial secretions.

Credit: GUDRUN HERZNER/PROC. NATL ACAD. SCI.

Larvae of the emerald cockroach wasp (Ampulex compressa; pictured) feed on the innards of the American cockroach (Periplaneta americana), but also have to contend with bacteria that live in their host's tissues. Gudrun Herzner at the University of Regensburg in Germany and her colleagues installed transparent panels into the sides of parasitized roaches and observed that the wasp larvae secrete large amounts of a clear liquid from their mouthparts onto their hosts' tissues.

Analysis of the liquid revealed the presence of the chemicals mellein and micromolide. These substances slow the growth of certain microorganisms, including the bacterium Serratia marcescens, which can kill insect larvae and was also isolated from the cockroaches.

Proc. Natl Acad. Sci. USA http://dx.doi.org/10.1073/pnas.1213384110 (2013)