Ceratopogonidae (Diptera) were collected on sheep farms in southern Ontario to establish whether Culicoides spp. pose a threat to the livestock industry. Specimens were collected in modified CO₂-baited Centers for Disease Control and Prevention light traps, returned to the laboratory, freeze-killed, and identified to species under a microscope. In addition to Culicoides variipennis (Coquillet), we found that Culicoides sonorensis Wirth & Jones occurred on a number of farms over a 2-yr period. These records represent a significant departure from C. sonorensis’ previously known geographical distribution. We present spatial and temporal distribution data for both species, with an emphasis on C. sonorensis. DNA sequence information is presented so that researchers lacking the necessary taxonomic skills can determine whether C. sonorensis is present in their collections. To differentiate C. sonorensis from C. variipennis, taxonomically reliable and informative traits were found in EF1a and, to a lesser extent, in ITS1, whereas the universal barcode region of cytochrome oxidase subunit 1 (CO1) was unsuitable.