Mosquito-borne diseases are of major public health concerns, mainly in tropical countries. Control of these diseases is primarily achieved through mosquito control. One of the major challenges encountered by mosquito control programmes is the development of resistance to insecticides by mosquitoes. Increased detoxifying activity through over expression of insect metabolic enzymes and altered target sites with decreased sensitivity to insecticides are the two major mechanisms of resistance. This review article presents our knowledge on development of insecticide resistance and the underlying biochemical and molecular mechanisms of resistance to major classes of insecticides. Techniques available to monitor resistance and to understand the underlying mechanisms are also discussed.

The spatial and temporal distribution of hosts is crucial in determining the feeding behaviour of hematophagous insects. We explored the spatial distribution of ornithophilic mosquitoes along the vertical axis in four locations covered with forests in Sri Lanka, i.e. Hanthana forest reserve (HAN), Halgolla forest reserve (HAL), Peradeniya university park (UOP), and Gampola (GAM). Mosquitoes were collected using bird-baited traps set at different height levels; 1 m (forest floor), 3 m (understory vegetation), and 6 m (canopy level), from 6.00-10.00 p.m. in 20 sampling sessions. Mosquitoes were identified using standard taxonomic keys and DNA barcodes of the cytochrome c oxidase subunit I (COI) gene. A total of 1212 mosquitoes belonging to 15 species and seven genera were collected and the highest numbers were reported from canopy level [HAN (219; 53.3%), HAL (93; 49.5%), GAM (136; 45.5%), and UOP (163; 51.7%)]. Culex pseudovishnui was the only species distributed evenly along the vertical axis. Although the mosquito abundance was significantly different along with three height levels, the diversity was not significantly different. Generalized feeders were common in patchy forests located close to human settlements and more specialized feeders were found close to natural forests. The findings of the study are important in understanding the interaction between ornithophilic mosquitoes with residing avifauna in each forest strata.