Reproduced from the Proceedings of the 77th Annual Meeting of the NJMCA. Please use the following citation when referring to this article:
Slaff, M. 1990. The biology of Culex salinarius. Proc. N. J. Mosquito Control Assoc. pp. 71-72 .
THE BIOLOGY OF CULEX SALINARIUS
MARC SLAFF
North Carolina Department of Environment, Health and Natural Resources, 310 East Third Street, Suite 200, Winston-Salem, NC 27101
ABSTRACT: Culex salinarius is a widespread mosquito that reaches greatest abundance along the Atlantic and Gulf Coasts of the United States. Larvae are found in fresh or brackish water that contains a great deal of emergent and decaying vegetation. Impoundments have been shown to be an excellent source ofCx. salinarius. Adult females of the species host seek within the first 2 or 3 hrs. after sunset, but may be active in non host-seeking pursuits just prior to sunrise. Studies have also indicated that Cx. salinarius appear to be most abundant at elevations of 20 ft. or more. In addition, they are indiscriminate in their bloodmeal preferences, and are efficient vectors of St. Louis encephalitis (SLE). Although Cx. salinarius apparently overwinter as inseminated adult females, the hibernaculae are difficult to locate. They do not, however, cease host seeking activities during the autumn as most Culex sp. do, and there is evidence that they obtain blood and exit hibernation in a parous state. This behavior may enable Cx. salinarius to harbor SLE and other viruses during the winter. A moderate level of autogeny has been noted with laboratory reared Cx. salinarius, but the extent of this occurrence in nature is unclear.
Controlling Cx. salinarius is difficult because the dense vegetation in their larval habitat offers protection from both predators and pesticides. They have an asynchronous life cycle and larvae are widely distributed, making a true assessment of immature population levels difficult. As a result, large numbers of adultCx. salinarius may be produced from what appear to be minimal larval numbers. In addition, the nocturnal activity of the species creates problems in both detection and control. Throughout much of the range of Cx. salinarius, the mosquito is overshadowed by day active salt marsh Aedes sp., even though the former is often more abundant.
DISCUSSION FOLLOWING THE PRESENTATIONQUESTION: Marc, is there a high percentage of interrupted feedings in Cx. salinarius?
SLAFF: I really cannot answer the question, but the answer may be important in the overwintering mechanism for SLE.
CRANS: Perhaps I can answer the question from what I remember of our host preference studies conducted during the 1960's. There would appear to be a high percentage of interrupted feedings in this species because we so frequently collect Cx. salinarius with very tiny blood meals. Most engorged mosquitoes have the abdomen fully distended but Cx. salinarius frequently show only a trace of blood. It is doubtful that the small bloodmeals we see would be enough to initiate egg production. As a result, I would interpret the small bloodmeal as an indication of an interrupted feeding.
QUESTION: Does that indicate that Cx. salinarius may be a timid mosquito that is easily interrupted during feeding?
CRANS: It may well be, however, interrupted feeding is difficult to measure with precipitin tests because we can only tell interrupted feeding by a mosquito that has fed on 2 very different hosts. If the bloodmeal is interrupted and the mosquito returns to feed on the same host species we would not be able to detect that in our tests. Our measurements of interrupted feedings come from mosquitoes that initiate the bloodmeal on one host and finish it on a different Class of animal, such as a deer followed by a bird or a bird followed by a rodent. To get a true indication of interrupted feedings you would have to dissect out the bloodmeals and count the number of peritrophic membranes in the gut.
QUESTION: Murphy found this species uniform morphologically but physiologically varied, didn't he?
SLAFF: I think he found slight differences in physiology but nothing he could identify with a taxonomic characteristic. Today we could do a gel pheretic study to see if there are genetic differences to indicate separate species or subspecies. This kind of work simply cannot be differentiated solely by morphology.