April 19, 2007 — Stink bug mating is so lengthy and lively that egg-colonizing parasites actually eavesdrop on it to their advantage, according to a new study.
The findings represent the first discovery of a parasite, in this case a wasp, eavesdropping on the vibratory sexual signals of another insect. Since some farmers use the parasite to control populations of stink bugs that feed on crops such as soybeans, the discovery might lead to better, natural pest removal methods.
It is possible the wasp evolved the ability to detect stink bug mating, since other creatures — including people — can't.
"Humans cannot hear stink bug vibratory songs without special equipment," lead author Raul Laumann told Discovery News.
Laumann, a scientist at Embrapa Genetic Resources and Biotechnology in Brazil, explained that both male and female brown Neotropical stink bugs vibrate muscles linked to their abdomen and thorax, before and during copulation.
Laumann and his colleagues obtained stink bug nymphs from a Brazilian laboratory colony. The researchers set the stage for mating by rearing the insects on a nutritious diet of sunflower seeds, soybeans, raw peanuts and green beans in a comfortable, humidity-controlled environment.
When the sexes were brought together and mating ensued, the researchers recorded the insects' vibrations. A loudspeaker outfitted with a plastic cone transmitted the vibrations to various parts of a green bean plant. For control purposes, the researchers also transmitted the sounds to polyester printer film. The female egg parasites were then placed on the plant or film.
The researchers found that female parasites oriented their bodies toward vibrations produced by female, but not male, stink bugs. Later, the parasites would preferentially station themselves on leaves where they detected the female stink bug mating movements.
