Larval black fly (Simulium vittatum) responses to chemical stimuli from predators and injured conspecifics under field conditions

We examined chemically-mediated antipredator behaviour in larval Simulium vittatum Zetterstedt 1838 by exposing individuals to one of five stimuli during daytime (1500 hr) and night-time (2300 hr) trials: distilled water, injured earthworm (Lumbricus sp.), injured conspecific (S. vittatum), predator (Corydalus sp.), and a combination of injured conspecific and predator. Larval responses were not homogenous with respect to treatment during daytime and night-time trials and the adjusted residuals show that a higher frequency of larvae curled in response to damaged conspecifics and the combination cue, and drifted when exposed to the combination cue. Additionally, the curling response was significantly longer when larvae were exposed to the three cues associated with predation. Lastly, larvae were more likely to drift at night in response to the combination cue suggesting that larvae responded differentially to chemical stimuli associated with predation and exhibited diel variability.