This study gives out the identification of insect faunal waves colonizing decomposing carrions of rabbits and guinea pigs treated with certain drug agent (tramadol) in Cairo, Egypt. Each of six rabbits and six guinea pigs is divided into 2 groups, where the first was killed by tramadol and the second group was killed by asphyxia as a control experiment. Generally, decomposition process was observed to have a slower rate in winter. Reaching to the skeletal stage was delayed in tramadol-intoxicated carcasses in comparing to the control carcasses. A total of 12966 arthropod individuals (Immature stages and adults) were collected. In concern of class Insecta, 67 species belonging to 6 Insecta orders and 2 Arachnida orders, 37 families and 51 genera were identified from this study during winter and summer seasons. Significantly lower numbers of immatures were observed and collected in the present study from the treated carcasses. The proportions of adult insects were also significantly different in control carcasses when compared with tramadol intoxicated ones in both winter and summer season for both rabbits and guinea pigs. This study provides background for the influence of tramadol on the colonizing wave of arthropod fauna which is of relevance to forensic science. We can conclude that drugs and toxins present in a decomposing body may alter the rate of insect invasion of that body.