Mosquitoes: Friends and Foes?

Published in Better Ways

Setting the record straight with a balanced view about mosquitoes and their place in the natural chain!

Mosqutio Mosqutio Photo: Sondre Dahle (reproduced with permission)

About mosquitoes

There are well over 3,000 species of mosquito, with more being found in great numbers all the time round the world. Mosquitoes, like flies, belong to the order named Diptera, because they have two wings. They belong to the family Culicidae and are classified in two main mosquitoes as pollinatorsgroups, Culicines and Anophelines.

Mosquitoes develop from eggs into worm-like larvae, which transform into pupae with a hardened outer skin, emerging in the end as fully formed male and female mosquitoes. Not long after emerging, once they have developed enough strength to fly adequately, the mosquitoes mate, after which the males die. The females feed up before laying their eggs, either on blood or nectar or sap, depending on the species. The eggs are laid in fresh, brackish or salt water, whether clean or polluted. Any standing water can be home to mosquito eggs, whether a natural pool, water butt or water collected in old car tyres or ruts in ditches, to name just a few. Culex mosquitoes lay their eggs in compact clumps, while the Anopheles group lays its eggs singly. Eggs can take just a few days or up to several months to hatch. The larvae which develop from the eggs mostly breathe at the surface of the water; some feed near the surface, while others find food deeper down. The larva transforms into a pupa, still living in the water, but no longer feeding. The adult mosquito comes out of the pupa and into the air after two to seven days, depending on circumstances. The whole life cycle takes between two and four weeks.

What are mosquitoes good for?

Mosquitoes suffer from a bad press, but they are not all bad!

- mosquito larvae in freshwater habitats help to purify the water by eating detritus: they have tiny brushes in their mouths which beat to create currents bringing in food particles, which are then transferred into their bodies

- some mosquito larvae feed on other insects

- mosquito larvae are food for dragonfly and damselfly larvae (nymphs), which live in their watery habitats for between two and six years, during which time they can consume enormous amounts of mosquito larvae as well as other small insects

- mosquito larvae are a food source for freshwater fish such as trout, perch, mosquitofish (gambusia affinis and gambusia holbrooki) and guppies (poecilia reticulata)

- killifish are small fish which eat developing mosquitoes in the egg, larva and pupa stages: when their numbers are highest, mosquito populations are greatly reduced. There are different types of killifish, which can live in fresh, brackish and salt water.

- adult mosquitoes are food for other species, notably bats, dragonflies, damselflies and insectivorous birds such as bee-eaters, all of whom have a voracious appetite for mosquitoes

- mosquitoes have a role in pollination: they feed on nectar (not just blood) and so can transfer pollen from plant to plant, as has been described in Norwegian researches; the North American Blunt Leaved Bog Orchid (Platanthera obtusata) provides a specific example

- the diverse roles and activities of mosquitoes, including night-time pollination, are being extensively researched, especially at the Smithsonian Institute in North America

Mosquitoes as pests

Mosquitoes are generally disliked and even hated by humans, because they bite. Mosquito bites can cause reactions ranging from mild irritation to severe allergic discomfort and, in some cases, disease. It is estimated that only about 3% of mosquito species carry zoonotic diseases (i.e. diseases which are dangerous for humans), but because of these, mosquitoes as a whole are targeted for annihilation in many countries, including Croatia.

In the HZJZ Yearbook for 2020 (in Croatian), where the figures for infectious diseases are given in item 5 'Zarazne bolesti u Hrvatskoj', malaria cases are given as 5 (imported); dengue fever cases: 3 (imported); West Nile fever: 0; Zika virus: 0. So the incidence of mosquito-borne diseases in Croatia is negligible, despite the rise in mosquito numbers reported in the initial monitoring, and the presence of potential disease carriers noted over the years.

Mosquito species as potential disease carriers which have been identified in Croatia according to factsheets issued by the European Centre for Disease Prevention and Control.

Aedes albopictus (Asian tiger mosquito): can carry dengue fever, chikungunya virus, dirofiariasis. This mosquito has been monitored in Croatia since 2016 (link in Croatian).

Aedes japonicus (East Asian bush or rock pool mosquito): possibly could become a transmitter of diseases such as West Nile fever, but is not considered a definite vector for disease transmission. Monitoring in 2016 and 2017 revealed that it was spreading in Croatian territory.

Anopheles atroparvus: can transmit malaria; possibly associated with West Nile fever. This species has been identified in Croatia.

Anopheles labranchiae: can transmit malaria. This species has been identified in Croatia.

Anopheles plumbeus: can transmit malaria. This species has been identified in Croatia.

Anopheles sacharovi: can transmit malaria. This species has been identified in Croatia.

Culex pipiens: can transmit West Nile fever and Usulu virus; possibly could transmit various other viruses. This species has been identified in Croatia.

Self-protection against mosquitoes

Note: the suggestions given here are based on the wide variety of personal experiences, including our own, which people have shared over the years. Always make sure that you do not use any substances, whether natural or chemical, in any way which can cause incidental harm to yourself, others, animals or the natural environment. Bear in mind that some essential oils are toxic to pets. If in doubt, seek professional advice. We accept no responsibility for misuse of the information we are sharing.

Personal protection

- Many foods create smells in our bodies which mosquitoes apparently don’t like, including garlic, onions, vinegar, chili peppers, lentils, beans and tomatoes, so eating them may help to repel mosquitoes.

- Many people find that taking a vitamin B supplement reduces the effects of mosquito bites, and indeed may make one less prone to get bitten.

- Avoid or at least limit alcohol, as drinking alcohol causes our bodies to release more carbon dioxide than normal, which attracts mosquitoes.

- Mosquitoes are attracted to lactic acid, which is produced when you sweat, and even from eating salty food: bathe or shower frequently if you are prone to sweating.

- Wear light-coloured clothing: mosquitoes are apparently attracted to darker colours.

- Using a fan may help to keep mosquitoes away from you.

- Natural repellent sprays which may help to protect your skin can be made from various essential oils individually by adding a few drops of the chosen substance to water in a spray bottle. Some essential oils can be mixed together for more potency: you can find numerous examples of homemade sprays on the internet and in herbal books. Always heed precautionary advice. In particular test a small area of your skin for allergy before applying any new concoction more generally on your body. Do not apply sunscreen before or after spraying your skin with an essential oil solution.

- Suitable scents which mosquitoes hate include tea tree oil, peppermint oil, mint oil, lavender oil, neem oil, citronella oil, tulsi (holy basil, ocimum sanctum) oil, lemon eucalyptus oil, cedarwood oil, lemon grass oil, castor oil, and cinnamon oil among others.

Around the home

- Use mosquito screens over windows, also nets around beds if possible.

- Do not leave lights on inside your home in the evening with the windows and doors open.

- Cloves and lemon: slice some lemons in half, insert cloves into each half and spread them around your home.

- Essential oil sprays can be applied round your home as well as to your skin.

- A garlic spray made by crushing some garlic cloves and boiling them in water, when cooled, can be applied around the home.

- A mixture of apple cider vinegar and witch hazel in equal quantities can be an effective anti-mosquito spray round the home.

- Candles scented with essential oils such as citronella can deter mosquitoes.

Outdoors

- Many birds feed on mosquitoes and other insects, so attracting them into your garden or on to your balcony can help control mosquito numbers.

- Never leave standing water in any kind of container (eg pots, old tyres), as these are ideal breeding grounds for mosquitoes. Spreading coffee grounds in puddles or stagnant water kills the mosquito eggs.

- Some plants repel mosquitoes, including basil, mint, feverfew, rue (ruta graveolens and ruta chalepensis), citronella and catnip, so they are good to plant in the garden or in pots around the outside of your home. (Note: some of these plants are skin irritants and can cause allergic reactions: They can also be very harmful if ingested by people or animals, so take care to keep them out of reach of very young children or puppies!)

- If you use an outdoor barbecue in the summer, burning some sprigs of rosemary or sage on it will help repel the mosquitoes.

Killing mosquitoes

In Croatia, measures to control mosquitoes were introduced several years ago. The Insect Control Programme has descended into a system of mass extermination of insects of all kinds using poisons which are potentially dangerous not only to the insects but to animals and humans. The result has been disastrous collateral damage. Mosquitoes have flourished while their natural predators have been decimated.

Extermination programmes using chemical pesticides don't work!

Many people use chemical insecticides in the home, without realising the potential harmful effects they might have on human health and the environment. You can check on the possible ill-effects of the active ingredients in many chemical insecticide products using our reference list ‘Pesticides and their Adverse Effects’.

We do not recommend killing insects, especially not with poisons. However, if you feel you have to, natural alternatives to chemical insecticides include garlic, camphor, pyrethrum and apple cider vinegar.

Information compiled by Nada Kozulić, Nicholas Haas and Vivian Grisogono, 2022.

NOTE: Many thanks to Sondre Dahle, senior engineer at the Norwegian Institute for Nature Research for permission to use his mosquito photograph. You can read about his researches in this interview.

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