Reproduced from the Proceedings of the 76th Annual Meeting of the NJMCA. Please use the following citation when referring to this article:
McNelly, J. R., and Crans, W. J. 1989. The larval habitat of Culex erraticus in southern New Jersey. Proc. N. J. Mosquito Control Assoc. pp. 63-64 .
JAMES R. McNELLY(1) AND WAYNE J. CRANS(2)
ABSTRACT: Culex erraticus is a mosquito species that is found primarily in the southeastern United States. New Jersey appears to be at the northern range for the species and little is known of the mosquito's biology and ecology in the State. Prior to 1988, all information on the biology of Cx. erraticus in New Jersey was obtained from resting box collections made by the Vector Surveillance Program of the N.J. Agric. Experiment Station. The seasonal data obtained from resting boxes, however, presented an anomaly.
Unlike other Culex, the adults never appeared in the resting box collections until late in July. After their first appearance, the species became relatively common and reached peak populations during August and September. The following year, however, Cx. erraticus was again absent from the collections until the month of July. Attempts to locate the larval habitat in the vicinity of the resting box sites were unsuccessful.
According to the literature, inseminated females of Cx. erraticus spend the winter in hibernation, an overwintering behavior that is also exhibited by the other Culex sp. in the State. As a result, one would expect Cx. erraticus to emerge from hibernation during the same time period as other Culex.
In 1988, the larval surveillance program of the Cape May County Mosquito Control Commission located numerous larvae of Cx. erraticus from two different sites during the month of July. Both sites were manmade ponds that were essentially devoid of emergent vegetation. However, both ponds had willow trees planted on the bank which produced dense root mats that extended into the water. Culex erraticus larvae were found in association with Anopheles quadrimaculatus within the extensive root system at both of the locations. The roots appeared to provide ample protection from the abundant fish population that were present in the habitat.
Beginning in October, 1988, the breeding habitat of Cx. erraticus in Cape May County was monitored to determine if habitat availability might explain the late seasonal appearance exhibited by this species. During the winter, snow melt coupled with spring rains raised the water level in each of the ponds to the point where the willow root habitat utilized by Cx. erraticus became totally submerged. In the early spring, the root mat was under at least a foot of water and was totally inaccessible to the adults as an oviposition substrate. We expect that as the water level drops during the warm summer months, the roots will refloat andCx. erraticus will again oviposit in the protected habitat. The observation does not explain how Cx. erraticus survives in New Jersey from May (when the adults should emerge from hibernation) to July (when the first larvae appear in the habitat). Resting box data, however, suggest that unavailability of breeding habitat may explain the late population peak for this species in New Jersey.
(1) Cape May County Mosquito Commission, P.O. Box 66, Cape May Court House, New Jersey 08210.
(2) Mosquito Research and Control, Department of Entomology, Rutgers University, New Brunswick, New Jersey 08903. New Jersey Agricultural Experiment Station Publication No. E-40101-02-89 supported by Hatch funds