The semiochemistry of the common North American pest of crucifers, Murgantia histrionica (Hahn) (the harlequin bug), and two related European species, Eurydema ventrale L. and E. oleraceum L., was investigated. The metathoracic scent glands of these warningly-colored stink bugs (Pentatomidae) are smaller than the scent glands of most cryptically-colored pentatomids, and the secretions from the scent glands of Murgantia and Eurydema species include two heretofore unknown natural products: (2E,62E)-octadienedial and (2E,6E)-octadiene-l,8-diol diacetate. It also was discovered that when harlequin bug adults are squeezed, they expel a frothy fluid from the margins of the prothorax with a distinctive odor due to the presence of 2-sec-butyl-3-methoxypyrazine and 2-isopropyl-3-methoxypyrazine. The presence of alkylmethoxyprazines in the expelled fluid of harlequin bugs extends the known distribution of these compounds to include the Heteroptera, and strengthens the argument that this class of pyrazines constitute a universal warning ordor equivalent to the color red as a visual warning signal.

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Author notes

1 This paper is dedicated to Dr. Murray S. Blum, University of Georgia, on the occasion of his retirement. The senior author wishes to thank Murray for letting him pursue his interest in bugs as a graduate student, and for all the encouragement over the years.

3 Mention of commercial products does not necessarily constitute endoresment by the USDA.

4 Department of Entomology, University of Maryland, College Park, MD 20742.

5 USDA-ARS, Insect Neurobiology and Hormone Laboratory, BARC-East, Beltsville, MD 20705.

6 Agricultural Entomology Institute, Perugia University, Borgo XX Giugno, 06100 Perugia, Italy.