LONGEVITY, FECUNDITY AND EMBRYOGENESIS IN BRAZILIAN APHIDS

Aphids cause great damage to cultivated crops. With the aim of aid man aging methods, biological properties subject to heavy selection were s tudied in the three south Brazilian species Schizaphis graminum, Sitob ion avenae and Rhopalosiphum padi (Homoptera: Aphididae). Changes in e mbryonic outer morphology were analysed under contrast phase microscop e and eight stages were described. The embryonic period terminated aft er 20, 24 and 26 hours; the longevity (expressed in number of days fro m nymph to adult death) was of 31.13+/-2.79, 29.73 +/-1.5, 25.13 +/-3. 22 and the fecundity (number of nymphs per adult aphid) was of 66.87 /-8.05, 31.67 +/-3.75, 49.53 +/-6.26, respectively. When the fecundity /longevity ratio was compared it was concluded that S. graminum was th e most dangerous to wheat, and BR-35 wheat strain was the most suscept ible to aphid control. The differences in embryonic time and morpholog ical characteristics can be used to classify the three species.