Concrete Urban Refugia for Culex quinquefasciatus, Impact of Summer Stressors, and Strategies Adopted to Oversummer.

Abstract

We carried out vector surveillance to locate adult sites of Culex quinquefasciatus, a filarial vector, during the summer in North Campus, Delhi University, Delhi, India. It revealed that the adults were a rare sight but landed naturally and assembled in indoor sites during the peak summer in 2016 and 2019. New adults repopulated some of these sites, after the removal of the samples. These adults were used to study the impact of summer stressors on their morphological, physiological, and behavioral traits, and strategies followed to oversummer in the urban environment. Adults adopted endophily, vagility, and staying at a lower height as strategies to avoid lethality. Females outnumbered the males, and showed morphological, physiological, and behavioral consequences; the majority were unfed. In females, sublethal effects such as aberrations of body parts including mouthparts; distorted oviposition pattern, reduced fecundity, and precocious tanning of retained eggs; and reduced egg hatch rate contributed to reduced survival and reduced reproductive output, thereby reducing vector load during peak summer. These are novel findings. Source reduction of adults during this period would provide effective eco-friendly control of this established species and should be part of the vector management strategies so that swarms of adults during monsoon could be prevented.