Biological parameters of two syrphid fly species Ischiodon scutellaris (Fabricius) and Episyrphus balteatus (DeGeer) and their predatory potential on wheat aphid Schizaphis graminum (Rondani) at different temperatures

Syrphid flies, Ischiodon scutellaris (Fabricius) and Episyrphus balteatus (DeGeer), are among the most common aphidophagous species in wheat growing areas of Punjab, Pakistan. Exploit predatory species efficiently in any biological control program requires an in-depth understanding of predator and prey interactions. The present study was conducted aiming to explore and compare the predatory potential of these predatory species against the wheat aphid, Schizaphis graminum (Rondani) along with their relative fitness at different temperatures in terms of duration of lifecycle stages under laboratory conditions. The shortest egg and pupal durations were observed at 33 °C, followed by 27 and 23 °C. Females of both species had longer life span (20.4 and 22.4 days) compared to the respective males (17.2 and 16.2 days). The pupal stage for I. scutellaris was significantly shorter than for E. balteatus at different temperatures; but statistically insignificant differences were found for any other life stage. The larvae of I. scutellaris consumed significantly more aphids (438.16) than E. balteatus (398.37) during their larval life span, and this difference was significant during the 1st and 3rd instars. However, the average daily prey intake of both species was found similar until the 10th day after hatching, and thereafter, I. scutellaris consumed significantly higher numbers of aphids/day. Obtained results may offer a baseline data for future conservation studies on biological control of aphids.