For many, it's a tough call - sex or sleep? But, for the millimeter-long nematode worm, Caenorhabditis elegans, the choice is a matter of straightforward chemistry. Writing in the journal Nature, Arthur Edison of the University of Florida, Frank Schroeder of Cornell University, Jagan Srinivasan, of California Institute of Technology and their colleagues, and co-workers at the US Department of Agriculture (USDA), describe how they used a highly sensitive NMR spectroscopy probe to identify tiny quantities of a novel group of pheromones from the soil-dwelling nematode that act as the organism's mating signal in times of plenty, but trigger hibernation when food is in short supply. There are countless nematode species that devastate crops and others are human gut parasites. The new study may lead to a better understanding of nematode biochemistry in general and one day to novel crop protection and anthelminthics for treating the parasites.