FIELD MORPHOLOGICAL VARIATION AND LABORATORY HYBRIDIZATION OF CULICOIDES-VARIIPENNIS-SONORENSIS AND CULICOIDES-VARIIPENNIS-OCCIDENTALIS (DIPTERA, CERATOPOGONIDAE) IN SOUTHERN CALIFORNIA

Two field populations of Culicoides variipennis (Coquillett) from sout hern California, C. v. occidentalis Wirth & Jones from the Salton Sea and C. v. sonorensis Wirth & Jones from a dairy wastewater pond in the Chino Basin, were sampled monthly from February to July (6-7 mo). Mor phometric analyses of slide-mounted adults reared from field-collected larvae and pupae indicated that females of the 2 forms were indisting uishable. Two of the standard characters, vying length and mandibular teeth, were correlated with seasonal temperature changes. Males of C. v. sonorensis were distinguishable by the presence of spicules on the aedeagus, which were entirely lacking in C. v. occidentalis. Two popul ations of C. v. occidentalis (Salton Sea and Bolsa Chica Marsh) and a laboratory strain of C. v. sonorensis hybridized successfully in the l aboratory and were maintained for 6 generations. Differential hybrid v iability (F-1) was observed in reciprocal crosses. Males of C. v. occi dentalis mated with females of C. v. sonorensis resulted in a lower eg g hatch (7.4%) than did the reciprocal cross (75.6%). Hybrid males dis played spicules on the aedeagus (a character of C. v. sonorensis), but the number of spicules was sometimes reduced compared with parental C . v. sonorensis (AA strain). Spicules in a field population of C. v. s onorensis were similar in number to the laboratory C. v. sonorensis-C. v. occidentalis hybrids. Based on successful hybridization, the 2 for ms should be considered closely related. The 2 forms are separated eco logically by the nature and distribution of their larval habitats.