The seasonal occurence and larval habitats of the mosquitoes of Corvallis, Oregon (Diptera-Culicidae)

Graduation date: 1964From May through November 1963, a mosquito survey was\ud made in the city of Corvallis, Oregon. The information\ud obtained dealt with the species of mosquitoes found,\ud their seasonal occurrence and the location and nature of\ud their larval habitats. A quantitative and qualitative\ud analysis of larval and adult mosquito collections by\ud genera and species was used to determine seasonal occurrence\ud and distribution.\ud Results reported here are based on a total of 309\ud light trap collections made in six locations, 29 aspirator\ud collections made in each of 11 diurnal resting sites and\ud larval surveys which were made every 10 days using the\ud dipper method.\ud During the course of the survey 6,968 specimens comprising\ud nine species and four genera were collected. The\ud species in order of abundance were Culex pipiens, Culex pens, Culex tarsalis, Culiseta incidens, Aedes increpitus,\ud Culiseta inornata, Anopheles punctipennis, Aedes vexans\ud and Aedes sierrensis. With the exception of Culiseta\ud inornata, a seasonal variation in abundance of all the\ud species favoring the late summer and early fall was observed.\ud Culiseta inornata was common during the spring\ud and early fall when temperatures were cooler.\ud Individual collecting techniques did not provide an\ud accurate, quantitative comparison of the relative abundance\ud of all the species. On many occasions when weather\ud conditions were ideal for mosquito activity, the number of\ud specimens that were taken in light trap collections were\ud not a true representative of the numbers present in the\ud vicinity. Culex pipiens and Culex tarsalis were taken in\ud large numbers in light trap collections but Aedes\ud sierrensis and Anopheles punctipennis were not present in\ud large enough numbers to indicate population trends. Conversely,\ud collections in diurnal resting sites included\ud large numbers of Culiseta incidens but very few Culiseta\ud inornata. The results of light trap catches however,\ud corresponded closely with catches in diurnal resting sites\ud as far as qualitative studies were concerned.\ud Routine larval collections from common breeding\ud habitats around the city were positive for all species\ud except Aedes vexans, Aedes increpitus and Aedes sierrensis.\ud These positive collections always confirmed the quantitative adult catches. The presence of the Aedes\ud species in the collections was probably due to adult infiltration\ud from breeding areas outside the city.\ud Larval habitats of the immature mosquitoes collected\ud were divided into two ecological groups. First, temporary\ud bodies of water which include rain pools, water troughs\ud and concrete structures and second, permanent bodies of\ud water including log ponds and sewage disposal ponds. All\ud these habitats gave rise to a number of generations during\ud the mosquito breeding season.\ud Mosquitoes collected from temporary habitats included\ud Culex pipiens and Culiseta incidens while Culex tarsalis,\ud Culex pens, Anopheles punctipennis and Culiseta inornata\ud were abundant in permanent habitats