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Abstract

The effects of crowding (intra-specific) as an extrinsic factor were studied on the corn-leaf aphid Rhopalosiphum maidis (Fitch). Larval (postnatal) and maternal (prenatal) artificial temporary crowding were carried out at different holding hours: 1(once), 3 (once), 3 (twice) and 24 (once). After postnatal crowding for less than a day during third larval instar: 3 h. (twice) crowding was the prime extrinsic stimulus affecting the larval survival. Crowding for 3 h (once) or twice) inhibited the adult emergence to 73.33%vs. 86.67% at 1 h (once)-crowding. Decreasing total longevity by increasing holding period was observed. Similar effect was also observed for the parturition period while the prenatal period reversely correlated to this sequence of crowding regimes. Natality/0 deceased by increasing holding periods. Some deaths were observed during the first three larval instars of the progeny by increasing crowding periods. More or less, various data were determined after the crowding of fourth (last instar larvae and teneral apterous mothers. Crowding for 1 h alatae among the first offspring while for 3 h (once) induced 12.22% alatae and for 3 h (twice) induced 15.88% alatae. Also, various responses of parental generation and its progeny were determined by crowding at different population density under short and long photo phases.