Under field conditions of Beni- Suef Governorate , field studies were carried out at the farm of Sids Agriculture Research Station during 2006, 2007 and 2008 cotton seasons to study the monitoring the first appearance and populations of adult males of both pink bollworm, Pectinophora gossypiella (Saunders) and spiny bollworm, Earais  insulana  (Boisd.) by using Delta pheromone baited traps. The average number of male moths of P. gossypiella per trap / week during the period from April till September during the 2006, 2007 and 2008 cotton seasons, In the first season 2006, had five peaks of abundance in 5^th May, 15^th June, 14^th July, 4^th August and 8^th September. In the second season 2007, also five peaks were observed. These peaks were occurred on 10^th April, 24^th April, 12^th June, 24^th July and 21^st August. While in the third season 2008, four peaks were observed on 1^st May, 29^th May, 31^st July and 4^th September. The average  number of male moths of E. insulana  per trap / week during the periods extending from March 17^th  till September 15^th , March 27^th  till 4^th September and April 3^rd  till September 18^th during the 2006, 2007 and 2008 seasons, respectively. In the first season 2006, four peaks of spiny bollworm were observed in 21^st April, 30^th June, 11^th August and 15^th September. In the second season 2007, five peaks were observed in 24^th April, 8^th May, 12^th June, 24^th July and 28^th August. While in the third season 2008, four peaks observed in 1^st May, 31^st July, 4^th September and 18^th September. The combined effect of the two main weather factors on the changes in the population activity of the pink bollworm moths explained by the percentages of variance of the two tested weather factors were significant during 2006 and high significant during 2007 season , respectively but in 2008 season, was insignificant. The correlation between the spiny bollworm population and the weather factors Max. and Min. temperature and average relative humidity, it is obvious that a simple positive correlation coefficient between the average number of captured male moths in sex pheromone traps and max. temperature was found, but this correlation was insignificant during 2006 and 2007 seasons and significant 0.38 (P= 0.08) in 2008 growing season. The combined effect of the two main weather factors on the changes in the population activity of the spiny bollworm moths explained by the percentages of variance of the two tested weather factors which was significant during 2006, but in 2007 and 2008 planting seasons it was insignificant.