Gonotrophic age structure of mosquitoes in the Culex pipiens complex (Diptera: Culicidae) and possible influences on host meal selection

L. O’Connor¹*, J. B. Gingrich¹, T. Unnasch² and H. K. Hassan²

¹Department of Entomology and Wildlife Ecology University of Delaware, Newark, DE 19716, USA.

²Divison of Geographical Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA.

*Corresponding author. E-mail: lindalou.oconnor@uky.edu. Tel: (689) 53.31.56

Accepted 8 October, 2009.

   Abstract

The age structure and mortality rates of Culex pipiens populations are critical to measures of vector capacity since each bloodmeal affords a chance of the female becoming infected. We examine the parous rate (proportion of females that had laid at least one egg boat) at two study sites to determine life-history parameters. Mosquitoes were collected using CO₂-baited CDC miniature light traps from June 15 to October 15 on a weekly basis from Cherry Island (2005 and 2006) and Cathedral Cemetery (2006). Thirty females were dissected per site per week, collections permitting. The parous rate remained below 50% through the end of July (mid-season). In early August, parity rates averaged 65 percent, but increased to approximately 80% by mid- to late August (late season) among non-diapausing, host seeking females. This increase in percent parity through August and September suggested populations are gonotrophically older in the latter part of the season. The mean parous rate approximation was used to age-independent survival rates. By late August, average daily survival rate was greater than 90% of the population and remained high through the end of the biting season. Parous individuals with a longer lifespan are more likely to be infected since they by necessity had a bloodmeal and are therefore more likely to acquire and transmit disease. 

Key words: Culex pipiens, parity, age-independent survival rate, gonotrophic age, host choice.