A total of 177,344 Culicoides specimens were collected from 3,109 light trap collections made weekly from August 1990 to October 1991 at 62 sites in the provinces of Cádiz, Córdoba, Huelva, Seville, and Málaga, Spain. Reported for the 1st time are Culicoides agathensis, Culicoides bahrainensis, Culicoides marcleti, and Culicoides odiatus in the Iberian Peninsula, and Culicoides scoticus in Andalusia, Spain. As a group, Culicoides were active throughout the year. The 3 most common species were Culicoides imicola (56,254), Culicoides newsteadi (24,359), and Culicoides circumscriptus (16,720). Numbers of C. imicola peaked in October, C. newsteadi peaked in May, and C. circumscriptus peaked in June. Based on regression analyses, the optimal minimum and maximum air temperatures, respectively, for adult insect activity were approximately > or = 18 degrees C and > or = 38 degrees C for C. imicola, 12 degrees C for C. newsteadi, 14 degrees C for C. circumscriptus (minimum temperature only), 16 degrees C and > or = 38 degrees C for "other" Culicoides, and 14 degrees C and 32 degrees C for total Culicoides. Optimal minimum and maximum temperatures could not be determined for Culicoides pulicaris, Culicoides punctatus, subgenus Monoculicoides, and the Culicoides obsoletus group. During August and September, the months when African horse sickness outbreaks occurred, C. imicola was the predominant species in the coastal Mediterranean zone. If the "other" Culicoides spp. group was not considered, the predominant species were C. imicola in the Guadalquivir River valley zone, C. newsteadi in the Subbética mountainous range zone, and subgenus Monoculicoides in the coastal Atlantic zone.