Introduction
Mosquitoes belong to the order Diptera and family Culicidae. They differ in their habitats which vary from species to species and also in the mode or time of biting. Only female mosquito sucks the blood which is required for its oviposition (WHO, 2005).

The period of development from egg to adult varies among species and is strongly influenced by ambient temperature. Some species of mosquitoes can develop from egg to adult in as little as five days, but a more typical period of development in tropical conditions would be some 40 days or more for most species (Vujic et al., 2010).

The seasonal variations directly affect the growth, development and activiteis of Aedes mosquitoes. In cooler climates Aedes develop in a week upto a month. It can remain in the larval stage for a month as long as water supply remains constant (Foster and Walker, 2002). In Thailand a study on the seasonal basis was conducted in dry and wet season respectively. In wet season the larval indices found to be greater as compared to the dry season (Preechaporn et al., 2007). The dynamics of seasonal population of Aedes mosquito was related to climatic factors as well as human activities in France (Poncon et al., 2007). In Serbia the results showed the highest number of mosquitoes was captured in May, June and July respectively (Vujic et al., 2010). A layer traps method was adopted to collect different mosquito species from August 2003 to June 2004. Aedes species was collected at the density of 12 eggs/layer trap/month. It was highest in rainy season that was a long period from April to July and a short is about from August to September. The mean annual temperature was 28℃ with an annual relative humidity averaging between 80% to 90% (Coulibaly et al., 2010). The adult female could lay upto 300~400 eggs during her life time (Matre-Pierre, 2006). The eggs of Aedes are desiccation resistant; this factor is of great entomological consideration because even during the dry season the eggs remain viable. Aedes species is very much susceptible to the climatic factors and seasonal variation. Some models and analysis had been represented to show the global scale association between climatic factors and development, potential distribution and population dynamics of Aedes mosquitoes (Hopp et al., 2001).

Culex quinquefasciatus is a major vector of lymphatic filariasis in Pakistan as well as in India (Jahan and Hussain, 2011). High population explosion of this species in Lahore District has become a severe biting nuisance primarily in summer months (Tahir et al., 2009). Weather pattern affects the adult female mosquito abundance by changing the quality and quantity of larval habits. The relationship between climatic variables and mosquito abundance can provide important information to determine virus activity levels and therefore disease risks (Wegbreit and Reisen, 2000). The Culex quinquefasciatus peaked during the winter months and in spring. Its egg rafts were found in a woody area. The population increased during March due to availability of favourable breeding sites containing stagnant water polluted with decayed organic matter. The species is most common in paddy fields and is related to the rice cultivation in India (Kanojia et al., 2003). Ovitraps were used in the summers of 2002 and 2003 to measure the oviposition activity of Culex mosquito. Oviposition pattern was similar in both years. It was highest in late June and the middle of July showed a steady decline throughout the remainder of each season (Jackson, 2004). An increase was observed in the population dynamics of all the mosquito species in the July-September period (Aldemir, 2004). Environmental temperature can also affect the ability of mosquitoes to transmit West Nile Virus (WNV) and an arbovirus (Dohm et al., 2002). For all the species of Culex population increased earlier and declined later in drier, warmer, Southern regions in California, these patterns may be driven by temperature (Barker et al., 2010).

Anopheles stephensi is the major cause of transmitting malaria not only in the Indian subcontinent but also in Iran and in middle east. Pakistan is facing the burden of about 1.6 million malarial cases annually. Anopheles stephensi transmits the plasmidium as an urban vector (The NEWS, 2012). Anopheles stephensi has increased in prevalence and became more common. This shift in species dominance may be due to the large-scale ecological changes that have taken place in the Punjab, where irrigation-induced waterlogging of soil with related salinization has created an environment favourable for the more salt-tolerant A. stephensi (Klinkenberg et al., 2004). A study was carried out from 1 April 1999 to 31 March 2000 in Lahore, Pakistan. Mosquitoes were collected from bedrooms using the pyrethroid spraycatch method and from vegetation and animal sheds using backpack aspirators An. subpictus populations peaked in August, September and October. High temperatures and low rainfall negatively affected seasonal abundance in our area. Our observations indicate that, in South Punjab, irrigation-related sites support the breeding of Anopheline mosquitoes, including the vectors of malaria (Herrel et al., 2004).

Present study was conducted out to: Identify all the species of mosquitoes found at the LCWU, Lahore campus; Locate the breeding sites for the mosquitoes in the university; Determine their population dynamics in different seasons; Co-relate their growth rate with the seasonal temperature.

Investigate the seasonal peaks for the growth of mosquitoes so that preventive measures could be adopted.

1 Results
Monthly Table of Mean values of Mosquitoes (Table 1~3).

Table 1 Monthly reading per trap

Table 2 Showing monthly the minimum and maximum temperature of Lahore

Table 3 Correlation coefficient (r) between different mosquito genera and mean maximum daily temperature

The analysis of variance of different mosquito genera collected in the month of October, 2011, revealed significant difference (F=6.27; df=2, 8; P<0.05). The mean comparison test (LSD) for different mosquito genera is presented in the Table 4. The results revealed that Aedes sp. (73.400) and Culex sp. (93.600) genera were the most prevalent, both were statistically at par, followed by genus Anopheles spp. (18.600). The analysis of variance of different mosquito genera collected in the month of November, 2011, revealed non- significant difference (F=1.41; df=2, 8; P>0.05). The mean comparison test (LSD) for different mosquito genera is presented in the Table 4. In the month of December and January, no population of mosquitoes was found in the campus. The analysis of variance of different mosquito genera collected in the month of February 2012 revealed non-significant difference (F=1.98; df=2, 8; P>0.05). The mean comparison test (LSD) for different mosquito genera is presented in the Table 4. The analysis of variance of different mosquito genera collected in the month of March 2012, revealed significant difference (F=11.97; df=2, 8; P<0.01). The mean comparison test (LSD) for different mosquito genera is presented in the Table 4, the results revealed that Aedes (877.60) and Culex (781.80) genera were the most prevalent, both were statistically at par, followed by genus Anopheles (474.60). The analysis of variance of different mosquito genera collected in the month of April 2012 revealed significant difference (F=66.32; df=2, 8; P<0.01). The mean comparison test (LSD) for different mosquito genera is presented in the Table 4, the results revealed that Aedes (1151.0) and Culex (858.25) genera were the most prevalent; both were statistically at par, followed by genus Anopheles. The analysis of variance of different mosquito genera collected in the month of May 2012 revealed significant difference (F=94.73; df=2, 8; P<0.01). The mean comparison test (LSD) for different mosquito genera is presented in the Table 4. The results revealed that Aedes (418.20) and Culex (343.70) genera were the most prevalent, both were statistically at par, followed by genus Anopheles.

Table 4 The mean comparison test (LSD) for different mosquito genera

Discussion
Present study indicates that different species of mosquitoes were present in LCWU campus including 3 genera of Aedes, Culex and Anopheles and species captured were Aedes aegypti, Culex quinquefasciatus, Anopheles stephensi and Anopheles subpictus. These species were related to the suitable breeding sites of LCWU where the seeping, drainage and dampness were present. Bamboo traps proved quite useful in capturing the larvae of different mosquitoes. The highest number of mosquitoes was found in the month of May because of suitable temperature and breeding environment. A highly significant difference was noted in these three genera in the month of March, April and May (P<0.05). So all these genera were abundant in these months due to favourable temperature.

The available data provides the seasonal fluctuations of the population dynamics of different mosquitoes. Statistical analysis reveals that the population of the genera of Aedes and Culex increases with temperature and of the population of Anopheles decreases. The hieghest density of Anopheles was found in the month of February. This study indicates the peak time of rising of the mosquitoes so that the proper precautionary measures can be taken before any outbreak of epidemic like DF or DHF. It is very important to know about the mosquito’s habit and seasonal abundance to control it properly.

Studies on the seasonal fluctuation of Aedes aegypti were undertaken in different localities of Delhi, during 2000. The Aedes aegypti population was found to be prevalent in all the localities in Delhi. Water coolers and tires were found to be the preferred breeding habitats of Aedes mosquitos in the city. Aedes aegypti, being hygroscopic, showed a phenomenon of annual pulsation. It tends to move to mother foci in the central areas of the city, which are humid in the dry season, and spread out during the wet season. Out of 103 778 houses surveyed, 20 513 houses and 3 547 containers were reported positive for Aedes aegypti. The house container and larval indices were very high during the post-monsoon season (Sharma et al., 2000). According to our study the rich abundance of Aedes aegypti was found in the months of March, April and May in LCWU, Lahore Campus. It is probably due to the suitable temperature for the breeding of mosquitoes. A spray named as K-Othrine EC15 was also applied in the Campus on 17^th May, so no mosquito larvae was found till the last week of May. The study showed that the highest densities of Ae. aegypti were recorded in the short dry season in Yopougon and Cocody, and at the beginning of the long rainy season in Adjamé and Treichville in the Gulf of Guinea. The lowest densities were recorded during the long dry season (from January to February) in all the five study sites (Coulibaly et al., 2010). We also record the lowest densities in the month of January to February. Even we found some of the population at the last week of February. Because the temperature in these months was about (12~14)℃ and it was not appropriate for the larval growth.

In an investigation, the highest density was observed from the rural areas of east and west Godaveri Districts of Andhra Pradesh, India. The highest density of Culex quinquefasciatus was found in September, October, December; the lowest were recorded in the months of April, May and June. High density of Culex is due to the presenceof big drains and cesspits in the villages: these are the breeding places chosen by Cx. quinquefasciatus (Murty et al., 2002). We recorded the maximum density of Cx. quinquefasciatus in February to May and the minimum was recorded in the months of December and January due to the low temperature. It was due the factor of hygienic conditions as well because in the Campus no water of rain was accumulated as in the fields or the rural areas of Godaveri Districts of Andhra Pradesh.

In Iraq a parasitological survey in 2002 identified no malaria cases but an entomological survey found Anopheles stephensi in high densities. The highest density was recorded in September and the lowest in December and January. A. stephensi adults were present during all months of the year except January, whereas. The highest number is both A. stephensi. The larval stages of A. stephensi disappeared in December and January when the mean temperature was below 14℃. Two peaks of the Anopheles larvae were seen: the first in June and the second in October (Ghoury et al., 2006). In our study we found the heighest density of Anopheles spp. In the month of February where the mean ambiant temperature was about 14.3℃. The results are in accordance with the study performed by Ghoury. Anopheles stephensi start building populations by end March, reaching a peak in April and May and thereafter start falling off rapidly till July. It is found in moderate numbers from September to November. In NWFP, Baluchistan this species is more prominent from July to September (Country Report Pakistan, 2003). The difference of population peaks of mosquitoes even in Pakistan is due to regional climatic changes, inadiquate sanitary conditions and rapid urbanization.

Materials and Methods
Material required
Bamboo traps half filled with water, rearing trays, dropper, convex lens, filter papers, paper cups and microscope.

Methodology
The 50 bamboo traps half filled with tap water were installed at LCWU campus. These traps were placed on different rich breeding sites of the mosquitoes because of being humid and shady. The sites were coded as A, B, C, D, E. Every site consisted of 10 traps. Weekly reading was taken from these traps and the samples were collected in paper cups carefully. The samples were then taken to the laboratory for identification, isolation and quantification of different mosquito species.

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