Phonoreception in some Coleoptera infesting stored products

Mechanoreceptors that could be phonoreceptive were located and studied in Sitophilus oryzae (L.), with preliminary tests also on Sitophilus granarius (L.). Tribolium confusum (Herbst), Attagenus piceus (Olivier), and Trogoderma inclusum LeC. Various behavioral responses of tethered (mounted) beetles were used as indices of reception of air-borne and solid-borne sounds of known frequencies and pound pressure levels. The probable receptors for air-borne sounds in S. oryzae are the well developed Johnston's organs in the second antennal segments, and tactile hairs on the bodies. Both are primarily sensitive to air movements or contact, and sounds are active only at relatively high intensities or in the near-field. The probable receptors for solid-borne sounds (vibrations) are chordotonal organs of the legs, which have relatively high sensitivity, and possibly the muscle receptor organs of the body wall. These four potential phonoreceptors are described and figured. The low sensitivity to air-borne sounds and high sensitivity to solid-borne sounds is probably related to the specialized habits of these insects.