Attractiveness of Tetragonula laeviceps (Hymenoptera: Apidae) to Citrus Volatile Compounds and Flower Colors in Indoor Microclimate Conditions

Abstract

Tetragonula laeviceps plays a vital role as a primary pollinator of citrus flowers for successful pollination. However, there is still a lack of understanding about how T. laeviceps can find citrus flowers. This study aimed to elucidate the factors influencing the attraction of T. laeviceps to citrus flowers, focusing on microclimate conditions, and visual and olfactory factors. For this, we conducted six-choice assays in a stingless bee house using artificial flowers as visual cues and citrus essential oils as olfactory stimuli. Three pairs of red or white artificial flowers were displayed to adult workers, with each pair placed in glass vials filled with diluted orange (Citrus reticulata) essential oil, lemon (Citrus limon) essential oil, or solvent. Simultaneously, microclimate conditions were measured, including temperature, relative humidity, and light intensity. We observed that the highest number of T. laeviceps visited the artificial flowers at 11:00, irrespective of visual and olfactory factors. We also found a positive correlation between the number of visits and both temperature and light intensity, whereas there was a negative correlation with humidity. The number of visits did not exhibit a significant difference between flower colors. In contrast, we observed the highest visitation to the orange essential oil, followed by the lemon essential oil and solvent. Gas Chromatograph – Mass Spectrometry (GC-MS) analysis revealed common terpenes in orange and lemon essential oils, while linalool and α-citral were predominantly detected in the orange essential oil. These characteristic terpenes could potentially be the attractants for T. laeviceps.