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Trevor Williams - página personal en español

Mosquitoes, Blackflies & Ticks (click here for publications in PDF format)

Species of Culex lay rafts of eggs whereas other genera lay eggs individually or in small groups.

Ovipisition in a Culex mosquito

The control of blood-sucking insects that transmit human and animal diseases remains a major challenge in many parts of the world, particularly in developing countries.

My work on mosquitoes (Aedes aegypti) and blackflies (Simulium spp.) has primarily focused on their relationships with viral pathogens (see section on
iridescent viruses) or control using a naturally-derived insecticide (see section on spinosad).  I have also collaborated in studies on saliva activated transmission of viruses by ticks.

More recently, I have become interested in habitat manipulation for control of Anopheles pseudopunctipennis, a vector of malaria in southern Mexico.  This work has been performed by J.G. Bond.



In Mexico, and many other parts of Latin America, the immature stages of An. pseudopunctipennis develop in river pools abundant in filamentous green algae (Spirogyra and Cladophora).

The algae represent an important food source and provide a refuge from predators for the mosquito larvae.


This relationship has been described in detail by Bond et al., 2005 (Ecol. Entomol. 30, 255-263).

As a result, ovipositing females select habitats based on the presence of these algae.

Extraction of algae from these pools results in a marked decrease in the densities of larvae and adult mosquitoes that lasts for 6 – 8 weeks.

This effectively eliminates the mosquito population during the period of peak biting activity of this species in southern Mexico.

For its simplicity and effectiveness, the intervention has now been incorporated into the Mexican Government’s Health Department guidelines on Epidemiological Monitoring, Prevention and Control (NOM-032-SSA2-2002).

Importantly, the intervention can be performed by local communities in affected areas.


Indeed, the technique has already been adopted in the State of Oaxaca where women from the community perform the extraction.

This study has been published - Bond et al. 2004. Proc. R. Soc. B 271, 2161-2169.

Filamentous algae provide food and refuges for mosquito larvae against predators.  As such, algae are important in oviposition site selection in certain species of female mosquitoes.

Filamentous algae form floating mats in riverside pools: ideal for the development of Anopheles mosquitoes.

Garden rakes were used to remove algae from pools of water for control of Anopheles pseudopunctipennis in Chiapas, Mexico.

Extraction of filamentous algae results in a dramatic reduction in Anopheles mosquito populations.


The subject uses a hand torch to locate the mosquito before aspirating it into the glass tube.

Human bait and UV light traps were used for monitoring the prevalence of biting adult female mosquitoes in areas subjected to the habitat manipulation intervention.

Studies on the environmental impact of the intervention have concluded that algal extraction results in minor changes in the diversity of aquatic insect communities.

Even important mosquito predators such as Odonata (dragonfly nymphs) are only transiently affected by the disappearance of mosquito prey items (Bond et al. 2006).

Treated areas fully recover their insect diversity in 3-4 months.

However, the magnitude of these changes is much lower than the natural (stochastic) variation in the aquatic community caused by year-to-year variation in rainfall and river discharge.


Click here for publications on arthropod vectors

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HOMEPAGEIridovirusesEcology of baculovirusesVirus insecticidesSpinosadPredators, parasitoids, pathogensOthersStudents


Trevor Williams - página personal en español