Seasonal abundance of Rhinoceros beetles, Oryctes spp. and Phyllognathus excavatus. were carried out under field conditions. Results obtained could be summarized as follows:- 1- Ecological studies on adult stage was carried out at kassassen district ,the following results were obtained * The seasonal abundance of adult stage was carried out by using light trap during seasons 1997, 1998 and 1999. The activity period of Oryctes spp. was extended from March/ April until December in all investigated seasons the highest activity numbers during October (1300individuals). Two times of activities at September (1187 individuals) and October (1300 individuals) the highest number of insects was trapped during season of 1997 followed by 1998 while the least was at 1999 with densities 1668, 1443 and 1271 individuals respectively. Activity period of Ph. excavatus extended from January until December in all investigated seasons the highest activity was recorded during October (860 individuals).Another activity period was at August (410 individuals). The highest number of insects captured in light trap was recorded during season 1997 followed by 1998 and the least at 1999 with densities of 1249, 915 and 726 individuals, respectively. male sex ratio of Oryctes spp. was 60.17 % in October, it increased to (65.76 %)in September ,while it was 58.81% for Phyllognathus excavatus in February but it increased to 60.85% in June. Simple correlation and partial regression values were positive and insignificant between Oryctes numbers and both minimum and maximum temperature where r value ranged (0.301 – 0.316 and 0.225 – 0.289 & b ranged (4.889 – 4.609 and 3.277 – 3.683) and E.v. % ranged (51.41 – 25.44 % and- 32.73 – 69.55 %) in all investigated seasons except during 1999, values were positive and significant effects where r ranged (0.459** - 0.490**), b ranged (4.096 – 4.381) and E.v. % ranged (91.5 – 34.61 %). While it was negative and insignificant for relative humidity, r = (0.068, - 0.116 and – 0.135), b = (2.694, - 2.247 and – 0.842) and E.v. % = (54.31 – 22.77 and 5.71 %).The explained variance percentage (E.v. %) on the number of captured insects was about 14.66 % for males while it was 21.93 % for female. In case of Phyllognathus excavatus, had positive and highly significant effects both Minimum and Maximum temperature where r value ranged (0.385**-0.388**,-0.457** – 0.525*** and -0.526*** – 0.466** & b ranged (0.057 – 0.067, 0.119 – 0.163 and 0.202 – 0.187) and E.v. % ranged [19.1 – 12.25 %, – 83.9 – 23.24 % and 18.3 – (– 45.4 %)] on the numbers of captures in all investigated seasons. While it was negative and insignificant for relative humidity, r = (– 0.243, – 0.372* and 0.164), b = (– 0.036, – 0.062 and 0.068) and E.v. % = (89.2, – 4 and 43.8 %).The explained variance percentage (E.v. %) was about 22.6 % for males, while it was 25.43 % for females.