Bionomics of Culex pipiens pipiens L., Culex restuans Theob., and Culex salinarius Coq. (Diptera: Culicidae) in central Iowa

Shipp, John
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The bionomics of Culex pipiens pipiens L., Culex restuans Theob., and Culex salinarius Coq. were investigated at Ames, Iowa in 1978 and 1979. Adult mosquitoes were collected using dry ice-baited CDC light traps, New Jersey light traps, suction traps, resting boxes, and sweeping, while egg rafts were collected from artificial pools. Culex mosquitoes were collected weekly from May to October to determine seasonal abundance, parity, and the time period diapause induction occurs;Collections of adult males and egg rafts were used to monitor the seasonal abundance of the three Culex species. Three thousand seven hundred and ninety, and 5,563 adult males and egg rafts were collected in 1978 and 1979, respectively. Seasonal abundance peaks of Cx. restuans occurred in spring and early summer. The population peak of Cx. salinarius occurred in the mid-summer while, most of Cx. p. pipiens were trapped in late summer and early fall;The number of adult female Culex collected in 1978 and 1979 was 4,363 and 14,235, respectively. The seasonal parity rate for the three species ranged from 19% in 1978 to 47% in 1979. The parity rate was highest in spring and decreased as the Culex population increased. The maximal number of gonotrophic cycles was two in 1978 and three in 1979;Diapause induction for adult female Culex was determined by the onset of hypertrophic fat deposits and by seasonal abundance of gravid Culex. Diapause induction began the first half of September. Ninety-nine percent of the mosquitoes in diapause were nulliparous;Electrophoretic studies were conducted on nulliparous and gravid females reared from field-collected egg rafts. Electrophoresis was used for species identification using aldehyde dehydrogenase (EC Fifty, 14, and 12% of nulliparous Cx. restuans, Cx. salinarius, and Cx. p. pipiens, respectively, had species specific enzyme patterns. Similar results were obtained with gravid mosquitoes;The staining intensity of bands was greater with gravid than nulliparous mosquitoes. Also, more isozymes were observed in gravid Cx. p. pipiens, and Cx. salinarius than in nulliparous females. The differences in the number and the increased concentration of isozymes may be related to the increased demand for energy production during egg maturation since, aldehyde dehydrogenase is tied to energy production;The studies on the biology of Cx. p. pipiens, Cx. restuans, and Cx. salinarius indicate that these species potentially play important roles in the natural history of SLE and WEE viruses in Iowa. The findings of the electrophoretic study show that the effect of the different physiological conditions of a mosquito species must be investigated if electrophoresis is to be an accurate taxonomic "tool" for species identification.