Status of insecticide resistance in anopheline mosquitoes of Punjab Province, Pakistan.

Susceptibilities of six anopheline mosquito species from nine localities in Punjab Province to DDT, dieldrin, malathion, fenitrothion, fenthion and propoxur were determined. DDT-resistance was found in An. annularis, An. culicifacies, An. stephensi and An. subpictus but An. nigerrimus and An. pulcherrimus were susceptible to DDT. Association between DDT-resistance and endophilic habit of the mosquitoes has been observed but needs further confirmation. Dieldrin resistance was present in all the six species. Five species were susceptible to malathion, and only An. stephensi showed incipient malathion resistance without cross resistance to other organophosphates. The six species were susceptible to fenitrothion and propoxur. An. nigerriums and An. subpictus showed some evidence of resistance to fenthion, the remaining four species were fenthion-susceptible.

A quantitative mosquito survey of 7 villages in Punjab Province, Pakistan with notes on bionomics, sampling methodology and the effects of insecticides.

A total of 451,337 female and male mosquitoes comprising 43 species in 9 genera were collected during a quantitative survey of 7 suburban and rural villages in the Lahore area during 1976 and 1977 using larval, indoor resting, outdoor resting, biting and light trap collections at weekly intervals. Culex tritaeniorhynchus was the most abundant species collected comprising 51.8% of the total specimens, followed by Cx. quinquefasciatus (16.4%), Cx. pseudovishnui (6.8%), An. subpictus (4.8%) and An. culicifacies (4.7%). Bovid bait collections provided the greatest diversity and highest numbers of mosquitoes per unit of collection effort, while light traps provided the poorest diversity and lowest numbers of specimens. Most species exhibited a bimodal seasonal abundance pattern, with peaks occurring in late spring and after the cessation of the heavy monsoon rains. The spraying of houses and cattle sheds with organophosphorous insecticides was effective in controlling the endophilic resting vectors of human Plasmodia, An. culicifacies and An. stephensi, but had little effect on the partially or completely exophilic resting species.

Observations on mating behavior and survivorship of Culex tritaeniorhynchus Giles (Diptera: culicidae) during late autumn.

Virgin Culex tritaeniorhynchus males and females from a laboratory strain and the progeny of wild-caught females were released at a rural village on the outskirts of Lahore during late autumn to study mating behavior in nature at a time when population abundance was declining. Although both released and endemic males were numerous, few recaptured females were inseminated. Apparently during late autumn there normally is a cessation of mating activity as the population begins to enter the overwintering diapause condition even though males and virgin females may be readily collected resting in fields. These data suggested that genetic material would not be readily introduced into the overwintering population during late autumn.

The influence of physiological age on the biting rhythm of Culex tritaeniorhynchus Giles (Diptera : Culcidae)

All of 704 Cx. tritaeniorhynchus females caught on bufflo bait were inseminated and 98 % were at ovariole stage 1. Parity rates ranged from 41 % to 66 % on the 4 nights studied with increases observed during dusk, midnight and before dawn. Changes in the parity of the biting population were related to sexual maturation, mating, oviposition rhythms and especially the survivorship of the adults.

The effects of climatic patterns and agricultural practices on the population dynamics of Culex tritaeniorhynchus in Asia.

Annual population curves for C. tritaeniorhynchus are presented for representative localities distributed from Pakistan, east through Southeast Asia and the Philippines and north to Japan and Korea. In the dry temperature (Pakistan) and colder maritime climates (Japan and Korea). C. tritaeniorhynchus populations apparently overwintered as hibernating adults, while in the warmer maritime climates (Okinawa and Taiwan), gonotrophic activity and larval development continued throughout the winter months. In these climatic types, the population curves closely paralleled the annual temperature curves. In the tropical climates, however, temporal population patterns were closely related to available moisture either in the form of annual precipitation and/or rice irrigation. The extremely variable environmental conditions tolerated C. tritaeniorhynchus throughout its distribution attests to the physiological and ecological plasticity of this species and suggests that further ecological and genetic studies may reveal marked clinical variances among selected biological parameters.