The effects of tide, temperature, rainfall, and salinity on the occurrence and abundance of immatures (instars and pupae) of the black salt marsh mosquito, Ochlerotatus taeniorhynchus (Wiedemann), were examined at a tidal pond in the Tijuana Estuary during 1996–1998. Immatures were found between May and early September. Tide had the greatest influence on immatures of this mosquito. Eggs eclosed when tides averaged 1.96 ± 0.10 (SD) m (1.83–2.19) 1–3 d before a flood tide. Eclosion averaged once every 14.4 d during 1996 (nine broods) and 1997 (eight broods) and once every 20.2 d during 1998 (six broods). Immatures were most abundant during late May-early August when tides were usually ≥ 2.0 m, and mean (±SD) pond temperature was 27.6 ± 2.6°C (23.8–33.9) and salinity was 44.6 ± 13.9 g/kg (33–95). Temperature primarily influenced egg diapause and influenced rate of development of immatures. Increased amounts of seasonal rainfall during 1997–1998 (42.9 cm: caused by El Niño), compared with 1995–1996 (11.4 cm) and 1996–1997 (17.3 cm), may have increased the mortality of overwintering eggs and/or diluted salinity of the substrate making it less conducive for oviposition.
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Vol. 40 • No. 4