Aspectos biológicos dos estágios imaturos de Pseudodorus clavatus (Fabricius) (Diptera: Syrphidae) alimentados com Schizaphis graminum (Rondani) (Hemiptera: Aphididae) em diferentes temperaturas

Abstract

Biological aspects of the predator Pseudodorus clavatus (Fabricius) fed on Schizaphis graminum (Rondani) were studied at different temperatures, in order to obtain information to be used in biological control of aphids. Eggs of the predator were individualized on sorghum leaf disks, kept in petri dishes and maintained at constant temperatures of 16, 19, 22, 25, 28 or 31°C, with 12h photophase. After larval hatching, nymphs and adults of S. graminum were offered to the predator ad libitum. The duration and survival of each instar, of the larva, pupa, and larva-adult were determined. The lower threshold temperature and thermal constant were also estimated. The mean duration of the development for the three instars of P. clavatus varied inversely with temperature. Reductions were observed in the duration of the larval stage (from 14.9 to 4.9 days), the pupal stage (from 17.2 to 4.2 days) and in the period from larva to adult (from 31.7 to 8.8 days), at 16°C and 31°C, respectively. The lower threshold temperatures were 10.8, 11.0, and 10.8°C for larva, pupa and larva-adult, respectively. Survival was above 78% for first-instar larvae, and above 94% for second- and third-instar larvae. The highest pupae and larva-adult survival were observed at 22°C and the lowest survival occurred at 16°C and 31°C. The complete development of P. clavatus, fed on S. graminum was achieved at all tested temperatures, that varied from 16°C to 31°C.