The Scent Glands and Their Chemicals in the Aposematic Cotton Harlequin Bug, Tectocoris-Diophthalmus (Heteroptera, Scutelleridae)

Abstract

In describing differences in morphology, developmental fate and secretion composition in the scent glands of the cotton harlequin bug Tectocoris diophthalmus we have sought to extend comparative knowledge of the scent gland system in the pentatomoid families within the Hemiptera-Heteroptera. Chemical investigation of the secretions was undertaken by coupled gas chromatography-mass spectrometry (GC-MS). The following volatiles were detected: 2-hexenal, 2-hexenyl acetate and 2- octenyl acetate from the metathoracic scent gland (an adult gland); nonanal from the abdominal dorsal first gland (the divided dorsal gland) in the adults; 2-hexenal, 2-octenal, 4-oxohex-2-enal, dodecane and tridecane from the abdominal dorsal second and third glands (the undivided dorsal glands) in fifth-instar nymphs. Secretory units are sparse, opener muscles absent, and secretion scarcely, if at all, present in the second and third dorsal abdominal scent glands in the adults. T. diophthalmus is an addition to the small but growing list of pentatomoids in which biochemical divergence of the abdominal dorsal first gland from the abdominal dorsal second and third glands has been reported. The metathoracic scent gland in T. diophthalmus is comparatively small, as it is in many other aposematic species within the Hemiptera-Heteroptera.