Fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith) is a destructive pest of corn. FAW invaded Egypt in May 2019 and was recorded for the first time in corn plantations in Kom Ombo - Aswan Governorate. Recently S. frugiperda C-strain was Confirmed in Nile corn plantation in Meet AL - Deeba village, (Qillin-Kafr El-Sheikh); while R-strain was confirmed in summer corn plantations of Abo Al- Gadeil, (Qillin-Kafr El-Sheikh) during corn season 2022.  Moreover, The R strain of S. frugiperda infested corn plants beside uninfected neighbourhood rice fields. This observation indicated that, R- strain of S. frugiperda preferred summer corn plants as a host than rice.
                Recent evidence of both strains collected from corn fields of Kafer EL Sheikh were identical morphologically and cause same damage symptoms.Biology of S. frugiperda C-strain and R-Strain were studied under natural conditions of field crop pests' laboratory at Plant Protection Research Institute Dokki, Giza, Egypt during Autumn and summer season (2022). C-strain larvae of S. frugiperda were fed on castor oil leaves. The average duration of life cycle and generation time at 23.0±2.0°c was 39.0±2.0 and 44.1±1.6 days, respectively. The corresponding averages for S. frugiperda R- strain corn - feed through early 3 instars at 28.0±2.0°c were 27.0±0. 5 and 29.0±0.6 days, respectively. The average of pre-oviposition periods {3.5±0.7 and 2.6±0.2 days} included the pre-mating period of 2.80 ±0.56 and 1±0.03 days for S. frugiperda C-strain and R- strain, respectively. The S.  frugiperda C- strain virgin females deposited infertile eggs when the pre-mating period increased more than 4 days at 26.0±2.0°c and 75.0±5.0 RH. These results are important for planning effective integrated control against fall armyworm to prevent it^,s rapid spread in Egypt.