Voracity of larvae, rate of development in eggs, larvae and pupae, and flight seasons of adults of the hoverflies Melangyna viridiceps Macquart and Symosyrphus grandicornis Macquart (Diptera: Syrphidae)

Abstract

AbstractThe voracity of larvae of Melangyna viridiceps and Symosyrphus grandicornis fed on the rose aphid, Macrosiphum rosae (L.), was measured at 10, 15 and 20°C. Over the three larval instars, a lifetime total of about 300 aphids (third‐instar equivalents) was consumed for a weight gain of 20 mg. Lifetime consumption was greater at lower temperatures. At 20°C, the third‐instar larva ate about 80% of the total, although this instar accounted for only 50% of larval development time. Melangyna viridiceps consumed more aphids than Symosyrphus grandicornis at 10 and 15°C. Development of eggs, larvae and pupae of both species was studied at constant temperatures of 4, 8, 10, 15, 20, 25 and 30°C. Although eggs hatched at 4°C, first‐instar larvae died at this temperature. A computer program (PMDS) was used to fit temperature/development functions for all stages. Linear, LoganTb, Stinner and exponential functions were fitted to the data. A day‐degree program, using the parameters given by PMDS and records of daily maximum‐minimum temperatures and data obtained from the field, suggested that the hoverflies might go through 10–13 generations per year in the field.