Exploring the Chemical Indole’s Effect on Black Soldier Fly Attraction and Oviposition Behavior

Black soldier fly (BSF) larvae are used worldwide for their ability to convert organic food scraps into valuable insect biomass and a digestate that can be used as a fertilizer and soil amendment. As such, BSF larvae are instrumental in the waste recycling industry. However, while there is considerable research dedicated to optimizing rearing of BSF larvae, very little is known about adult BSF behavior. Understanding adult behavior is valuable because it could improve adult mating and egg laying in rearing operations, ultimately leading to increased BSF production and more waste recycling. In this study, we tested whether addition of an attractive compound (indole) to an egg laying substrate would increase adult fly oviposition. We used a cage assay to measure BSF oviposition and landing rates when nearby indole. We documented the frequency that the BSF landed on wooden cutouts treated with indole and weighed the eggs left in those cutouts. Analysis of the results revealed that there was no statistically significant difference in BSF landing rates between indole-associated and control cutouts. However, BSF females laid significantly more eggs in indole-associated cutouts compared to control cutouts. These findings suggest that indole addition to the oviposition area does not increase the number of flies visiting, but does increase the number of eggs laid by flies that do visit the site. As such, it is important to examine not just attraction but also post-landing behavior, such as egg laying, which can also be influenced by chemical cues.