Olfactory response of the lady beetle Hippodamia convergens (Coleoptera: Coccinellidae) to prey related odors, including a scanning electron microscopy study of the antennal sensilla

The olfactory ability of the convergent lady beetle, Hippodamia convergens Guerin-Meneville, was investigated using an 8-arm airflow olfactometer. Lady beetles tested were normal or had their antennal tips, or maxillary palps amputated. Normal beetles and those with their maxillary palps removed were highly attracted by the odor of radish leaves infested with green peach aphids, Myzus persicae (Sulzer). Beetles with their antennae or antennal tips removed were not attracted. In addition. the normal lady beetles were significantly attracted to clean radish leaves. These results indicate that H. convergens can perceive olfactory stimuli released their prey and their prey's host plant (or a combination of the two) and that the beetles' olfactory receptors are located principally on the tips of their antennae. Also as part of this study, the antennal sensilla of male and female convergent lady beetles were examined using scanning electron microscopy. The sensilla were counted the majority of which were located on the terminal segment, and 4 morphological classes were identified: chetiform, Bohm, basiconic, and trichoid. Chetiform sensilla were observed on all 11 antennal segments, while the Bohm sensilla were located only on the first two segments. The basiconic and trichoid sensilla were located exclusively on the terminal two segments. The most abundant sensilla on the terminal segment, trichoid sensilla, were suggested to function in olfaction.