An experiment was conducted to determine the effect of crowding on: larval and adult survival; larval stadia duration; sex ratio of adults; reproductive capacity of adult female Dendroctonus ponderosae Hopkins. To investigate distribution of the effect of crowding within a single age group, newly hatched larvae were used. The responses of these larvae and subsequent adults were observed after exposure to densities of 1, 3, 6, and 9 larvae (or adults) per unit of food supply for each of 3 time intervals. Survival of 1st-stage larvae increased as crowding increased. Survival at the adult stage increased in Crowd 3, decreased in Crowd 9, and was not consistent in Crowd 6 as crowding duration lengthened. The rate of survival decreased as either crowding level increased or duration of crowding lengthened. Crowding influenced the rate of larval development, which in turn influenced sex ratio; i.e., as the 3rd and 4th larval stadia became shorter, more females and fewer males survived. Thus, the theoretical ratio of 1:1 shifted in favor of the female. The reproductive capacity of the female adult decreased as larval crowding increased. There was an apparent feeding stimulus through association that resulted in greater than 60% successful establishment of 1st-stage larvae when crowded.