Studies of Predators of the Balsam Woolly Aphid, Adelges piceae (Ratz.) (Homoptera: Adelgidae) VIII. Syrphidae (Diptera),

Abstract

Several species of native syrphids have been found to prey upon the introduced balsam woolly aphid, Adelges piceae (Ratz.), in New Brunswick and three of these, Syrphus torvus O. S., Metasyrphus lapponicus (Zett.), and Neocnemodon coxalis (Curr.), are sometimes very common. As part of a long-term study of the biological control of the balsam woolly aphid by native and introduced predators, the life histories, natural control, population fluctuations and control value of these native syrphids have been investigated.

Seasonal natural history of aphidophagous Syrphidae (Diptera) attacking the balsam twig aphid in balsam fir (Pinaceae) Christmas tree plantations

“…In our study, the two species of Eupeodes showed this behaviour and pupae were exclusively found on foliage of balsam fir trees. Brown and Clark (1960) also observed this behaviour for E. lapponicus on balsam fir trees infested by the balsam woolly adelgid. Differential niche selection is an important mechanism that permits species coexistence (Rosenzweig 1981; Berthiaume et al .…”

“…Larvae of D. venustus can feed on aphids, but these may not be their preferred prey (Vockeroth 1992). The three other species confirmed here as predators of balsam twig aphid are known as aphid predators (Vockeroth 1992), and larvae of S. torvus and E. lapponicus have been reared with aphids collected on balsam fir trees (Brown and Clark 1960; Vockeroth 1992).…”

“…However, the nine other species reported as adults by this author were not confirmed as balsam twig aphid predators in our study. Syrphid predator diversity is expected to vary spatially and temporally (Banks 1959; Brown and Clark 1960; Pollard 1971; Niehoff and Poehling 1995). The low abundance of D. venustus is consistent with the fact that this species is not considered as a specialist aphid feeder during larval development, contrary to the three other species associated with the balsam twig aphid in this study (Vockeroth 1992).…”

“…Syrphus torvus pupae were found on the top or in crevices of the upper ground litter under balsam fir trees. In a study of predaceous Syrphidae attacking the balsam woolly adelgid ( Adelges piceae (Ratzeburg); Hemiptera: Adelgidae) in New Brunswick, Brown and Clark (1960) also observed that pupae of S. torvus were always found on the forest floor, where several other species of Syrphidae are also known to pupate (Clark and Brown 1959; Schneider 1969; Hovemeyer 1992, 1995; Mitchell and Maksymov 1977). These species appear to need the moist soil environment to form their puparia (Mitchell and Maksymov 1977).…”

“…These species appear to need the moist soil environment to form their puparia (Mitchell and Maksymov 1977). Other species of predaceous Syrphidae rather pupate in close proximity to where their prey feed (Brown and Clark 1960; Schneider 1969; Vockeroth 1992). In our study, the two species of Eupeodes showed this behaviour and pupae were exclusively found on foliage of balsam fir trees.…”