Biological control of Diatraea saccharalis is regarded as one of the best examples of successful classical biological control in Brazil. Since the introduction of the exotic parasitoid, Cotesia flavipes, from Pakistan at the beginning of the 1970s, decrease in D. saccharalis infestation in sugarcane fields has been attributed to the effectiveness of this agent. Recently, the native Tachinidae fly parasitoids (Lydella minense and Paratheresia claripalpis) have also been implicated in this success. However, quantitative data confirming the actual contribution of these agents to the control of D. saccharalis are rather limited. The purpose of this study was to investigate the dynamics of the interactions between D. saccharalis and its parasitoids, emphasizing the temporal patterns of parasitism. To investigate this question, a large data set comprising information collected from two sugarcane mills located in the state of Sao Paulo, Brazil (Barra and Sao Joao sugarcane mills), was analysed. Basically, the data set contained monthly information about the number of D. saccharalis larvae and their parasitoids in each sample (man-hour per sample), the sugarcane varieties cultivated, the age of the sugarcane plants (only at the Sao Joao sugarcane mill) as well as the sugarcane cut at sampling time. The data were collected from March 1984 to March 1997 and from May 1982 to December 1996 for the Barra and Sao Joao sugarcane mills, respectively. Temporal inverse density-dependent parasitism was predominant for both parasitoid species with respect to all spatial scales. Although the temporal pattern of parasitism was not directly density dependent, it was evident that the tachinids and C. flavipes presented positive numerical responses according to variations in D. saccharalis densities through time. Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Habitat; Man made habitat; Land zones; Neotropical region; South America Tachinidae; Cotesia flavipes (Braconidae ); Lepidopteran hosts; Diatraea saccharalis; Prevalence; Cultivated land habitat; Brazil; Sao Paulo; Prevalence in lepidopteran hosts, temporal patterns, influences, sugarcane fields Diatraea saccharalis (Pyralidae); Dipteran parasites; Tachinidae; Hymenopteran parasites; Cotesia flavipes; Prevalence; Cultivated land habitat; Brazil; Sao Paulo; Dipteran & hymenopteran parasites prevalence, temporal patterns, influences, sugarcane fields none