We examined the effect of augmenting black light trap with CO₂ at two release rates for monitoring and surveillance of Culicoides at northern latitudes. Species composition was highly correlated among black light (BL) traps with no CO₂ (BL0 traps) and traps augmented with 300 and 1000 ml/min CO₂ (BL300 and BL1000 traps, respectively); however, traps augmented with CO₂ captured one to three more rare species than BL0 traps and can detect rare species that might be missed if BL0 traps were used. Addition of CO₂ increased the number of individuals captured from 1.4 to 38.5—fold for BL300 traps and from 1.5 to 153.5—fold for BL1000 traps. This advantage may be lost in areas with low abundance as might be expected at the limits of species.The daily probability of detecting a species was greater for traps augmented with CO₂, but this can be compensated for by operating BL0 traps for sufficient time. The association between numbers captured by BL0 and BL300 and BL1000 traps also suggests that BL0 traps may provide useful measures of relative abundance for Culicoides sonorensis, Culicoides davisi, and Culicoides riethi, again providing the BL0 traps are left to operate for some period. Measurements of diel activity were influenced by trap type only for a single species and were primarily determined by solar radiation, temperature, and windspeed. Overall, the use of BL0 only traps for widescale surveys is supported, especially given their convenience.