188 Separation of Variable Culex territans

The siphon indices, branching of setae 5-C and 6-C, lengths of 5-C compared to the lengths of 6-C, length of the most proximal seta 1-S compared to the siphon length, and the occurrence of a paler abdominal segment IV were compared among Culex apicalis, Cx. boharti and Cx. territans larvae. These characters in Cx. territans were found to be much more variable than previously recognized, and often overlapping completely with these characters in Cx. apicalis and Cx. boharti. The use of male genitalia characters on reared adults from larval collections is the best means of separating these species, particularly where they are sympatric or in close proximity. INTRODUCTIONANDBACKGROUND This is a report of a study of certain morphological variations found in Culex (Neoculex) territans Walker, and of characters used to separate this species from several other species with which it can be confused: Cx. apicaiis Adams, Cx. boharti Brookman and Reeves, and Cx. reevesi Wirth. The study of natural variations occurring in Culex territans is important as this species is the type by original designation (Dyar 1905) for subgenus Neoculex Dyar. This subgenus was reclassified by Sirivanakarn (1971) and reduced from approximately 70 to 25 species (6 North and Central America, 13 Australasian, 5 European-Mediterranean and 1 Japan-Korea-USSR). Since then at least one new species has been described, from Venezuela. Also, Cx. territans is the only species in Neoculex with an exceptionally wide distribution, i.e., Nearctic and Palearctic. The type of Cx. territans is non-extant (Belkin 1968, Knight and Stone 1977) and the type locality is listed as “United States” in Knight and Stone (1977). However, Belkin et al. (1966: 3, 19) restricted the type locality to the vicinity of Charleston (Charleston County), South Carolina. ’ 6516 40th Avenue, University Park, MD 20782. 2 Walter Reed Biosystematics Unit, Department of Entomology, Walter Reed Army Institute of Research, 3 Washington, DC 20307-5 100. The views of the authors do not purport to reflect the positions of the supporting agency. Mosquito Systematics Vol. Zl(3) 1989 189 This study was initiated because of Cx. territans larvae submitted to the Walter Reed Biosystematics Unit (WRBU), or previously seen by the authors, which exhibited apicalis-like or boharti/reevesi-like characters. Two types of larval variations were observed in Cx. territans that seem to cause the majority of identification problems: (1) larvae with an exceptionally long siphon more like that classically attributed to Cx. apicalis; and (2) larvae with abdominal segment IV paler than segments III and V (banded larvae) that would key to Cx. boharti or Cx. reevesi in Bohart and Washino (1978) and Cx. boharti in Darsie and Ward (1981). Variation in the siphon index of Cx. territans has not been defined previously, but has been listed as about 7 (Carpenter et al. 1946), 6 to 7 (Bohart 1948), usually 6-7 (Mattingly 1953), 6 to 7 (Carpenter and LaCasse 1955), about 6 (King et al. 1960), less than 7 (Chapman 1966), about 6 l/2 (Gjullin and Eddy 1972), not given (Bohart and Washino 1978), 5 to 6 (Wood et al. 1979) and usually less than 7 (Darsie and Ward 1981). MATERIALS AND METHODS We assume that previous authors were all using the siphon index in the classical sense, i.e., the length of the siphon (minus the siphon acus at the base and the spiracular apparatus at the apex) divided by the width at the base, not that used by Belkin (1962) and Harbach and Knight (1980). In this study we used the classical index described above and as used by Harbach (1988). Specimens examined include larvae and adults identified by the junior author from the mid-Atlantic and southern states over the last 24 years, and larvae and adults currently deposited in the mosquito collection of the National Museum of Natural History, Smithsonian Institution, Museum Support Center, Suitland, Maryland. Over 370 larvae, 200 adults and 150 male genitalia in this collection were examined from 25 states. RESULTS AND DISCUSSION Table 1 clearly shows that the siphon indices for Cx. territans listed by the above authors are gross underestimates. Based on our measurements of the siphons of 221 Cx. territans from 23 states (Table 2), Cx. territans not only has a wider range in its index than Cx. apicalis, but also can have a higher index. The mean index for Cx. territans, however, is lower than that of Cx. apicalis. Based on our measurements of Cx. territans throughout its distribution, we conclude that the siphon index is of no value in separating Cx. territans from Cx. apicalis, except possibly in areas where they are sympatric, or nearly so (Arizona, California, Nevada, Oregon and Texas) (see Darsie and Ward 1981). Chapman (1966) very astutely reported, “While larvae of apicalis and territans are easily separated by eye in the West, the characters used in keys to differentiate these species, i.e., the length and shape of the siphon and relative length of siphonal hairs to length of siphon, are not tenable on a nationwide basis. The writer has collected territans larvae from Florida that possess the above mentioned characters supposedly indigenous to apicalis.” A comparison of the siphon indices of these two species is needed from areas of sympatry. Only four specimens of Cx. territans were ,