Background and Aim: Mosquitoes are the most important vectors of disease in the world which transfer important diseases such as malaria, yellow fever, dengue fever, and F ilariasis to human. Today, living in the suburbs, slums, and non-standard housing conditions has increased which, in turn, has brought with it ecological changes and manipulation of nature . These transformations have prepared the conditions for growth and proliferation of disease causing vectors. This study was designed to study the biology of mosquitoes in Gonabad city so that in case of danger appropriate measures could be taken to fight them in the shortest period of time.

  Material and Methods: This descriptive study was conducted in four rural districts, namely, Darb-e Sufeh, Kureshk, Shehab and Senjedak. The mosquitoes were collected every fifteen days from April to September 2008. Sampling for mosquito larvae and Pope was done through ladle handling method and to catch adult mosquito, light traps and hand fishing method were used. The mosquito collection was performed in the shelters and environments surrounding larvae sites. The collected samples were transferred to the laboratory to determine the species, and they were identified using a stereomicroscope or Binocoler based on Iranian guide for identifying mosquitoes.

  Results : In total, 230 samples of mosquitoes (170 larvae and 60 adults) were collected with three methods of ladle handling, hand catch, and light trap for which three species of Anopheles superpictus, Culiseta longiareolata, Culex pipiens were identified. Their abundance was as follows: An. superpictus 10 larvae (4.34%), Cu. longiareolata 160 larvae and 50 mature larvae (91.32%) and Cx. pipiens 10 adult (4.34%) and their activity peak was from May to July.

  Conclusion: Regarding the species collected and the fact that these mosquitoes are considered the most important vectors of malaria and viral diseases, it is necessary to educate people about vector borne diseases in these areas.