MV Blog

DISPLAYING POSTS TAGGED: mosquitoes (1)

Bug of the Month - the mosquito

Author
by Tim Blackburn
Publish date
4 February 2013
Comments
Comments (2)

Mosquitoes are midge-like flies comprising the family Cucilidae. There are over 3,500 species of mosquito described worldwide and most of these require vertebrate blood as the principal portion of the female diet. The blood provides protein for egg development and maturation, and the lipids it contains are an energy source. Females possess elongated piercing and sucking mouthparts for obtaining their blood meals. Males obtain all their energy from sweet fluids such as nectar and honeydew. Since they don't lay eggs, male mosquitoes do not require a protein source and do not bite.

Close-up of female mosquito The elongated proboscis of this female mosquito enables it to obtain the protein it requires for egg development and maturation.
Image: sondebueu
Source: sondebueu via cc
 

Adult females lay eggs in or near water, commonly on vegetation, a few days after a blood meal. The life cycle includes four larval stages, or instars. Between each instar the larva moults in order to grow. The larvae, or 'wrigglers' (so-called due to their characteristic movement), typically inhabit stagnant water bodies, and must come to the surface periodically to breathe through spiracles or a siphon. The larvae of some species use their mouth bristles to filter water for microorganisms, while others scrape food particles off the surfaces of submerged objects. The pupa does not feed but must come to the surface to breathe through respiratory trumpets.

mosquito larva The mouth bristles, used in filter feeding, are clearly visible on this wriggler. Note also the three body segments and the segmented abdomen.
Image: Tim Blackburn
Source: Museum Victoria
 

Female mosquitoes inject saliva that contains an anticoagulant into their host to prevent blood-clotting. The saliva also contains components that cause vasodilation (to increase blood blow) and suppress the immune response of the host (to protect the mosquito). Once the feeding episode ends, the host produces antibodies which trigger a release of histamine. This in turn increases the permeability of adjacent blood vessels, thereby enabling a stronger immune response. The blood vessels swell and this causes the familiar, itchy lump—the 'mozzie bite'.

Female mosquito A female mosquito just after landing on my toe as it commences a blood meal. Note the thin abdomen at the start of the meal.
Image: Tim Blackburn
Source: Museum Victoria
 

Female mosquito feeding The same mosquito one minute later. Note the swollen abdomen which is red because it is full of my blood.
Image: Tim Blackburn
Source: Museum Victoria
 

Viruses and pathogens are easily transferred between mosquito and host via the saliva. Mosquitoes are serious agents in the transmission of diseases such as dengue and yellow fever, malaria and lymphatic filariasis. In 1996, the World Health Organisation estimated that several million people die each year from mosquito-borne diseases around the world. Each disease is spread by a specific type of mosquito; malaria is spread by Anopheles spp. and dengue fever is primarily spread by Aedes aegypti.

However, mosquito-borne diseases are rare in Victoria, and mosquitoes here are more likely to annoy rather than cause disease. You can prevent bites by wearing insect repellent and protective clothing, and removing breeding sites. Window mesh and mosquito nets also help exclude potentially harmful species, particularly in tropical and subtropical areas. Various plant species such as Citronella Grass, Rosemary, Catnip and Marigolds repel mosquitoes and may be especially useful if planted near doorways and windows. 

Links:

CDC: Mosquito-borne diseases

Vector-borne diseases in Victoria

About this blog

Updates on what's happening at Melbourne Museum, the Immigration Museum, Scienceworks, the Royal Exhibition Building, and beyond.

Categories