The museum is currently closed for roof works. Click here for reopening dates and information.

January 2021

Not all mosquitoes bite!

Can you identify this mosquito and tell me whether it’s male or female? Is this the species that has the predatory larvae?

Answer

An adult male Toxorhynchites speciosus mosquito. Photo: Lawrence Milton. Toxorhynchites speciosus adult feeding from a flower. Photo: © Geoff Thompson. Toxorhynchites speciosus larva eating a wriggler. Photo: Colleen Foelz.

This is the giant mosquito known as Toxorhynchites speciosus. The feather-like antennae indicate that this is a male. The adults of both sexes gain their nutrition from plant juices and nectar — they don't bite us! These mosquitoes are very large, about 8 mm in length, similar in size to the biting Scotch Grey (Aedes alternans). They have very long striped legs, a long curved proboscis (designed for feeding from plants rather than sucking blood) and an iridescent body. When it’s time to lay eggs, the female hovers above a small water body and shoots them out onto the surface.

The so-called ‘wrigglers’ that hatch out of the eggs are the larval stage of mosquitoes. And yes, these wrigglers are voracious predators and actually eat the wrigglers of the mozzies that do bite us!! They grow larger than normal wrigglers and have a 'hairy', reddish appearance. The hairs on the body, called ‘setae’, are sensory and are thought to help the larvae locate their aquatic invertebrate prey.

They breathe through a siphon on their abdomen, much like having a snorkel on their rear end. Unfortunately these beneficial mosquito wrigglers often get thrown out when bird baths and dog bowls are emptied. There have been attempts to use T. speciosus wrigglers in the biological control of biting mosquitoes but they have not proven successful.

The length of the larval period depends on temperature and food availability. After this feeding phase is complete, the larva transforms into a curled, non-feeding pupa. Changes occur inside the pupa as metamorphosis proceeds and it remains motile. When the time is right, the pupa rests at the surface of the water, the external casing splits and the adult mosquito emerges.

The mosquitoes that bite us are females requiring a blood meal to provide the nutrition needed for egg development. In T. speciosus, the protein and fat gained during the predatory larval stage means that the adult females don’t need to undertake the risky behaviour of biting and sucking the blood of a vertebrate such as ourselves. Instead you’re likely to find these mossies on a flowering plant obtaining nectar and other plant juices.

This all-round ‘good’ mosquito is widespread along the coast from the Northern Territory through eastern Australia, extending south along coastal New South Wales. Worldwide nearly 100 species have been described in the genus Toxorhynchites.

 

In the movie ‘Jurassic Park’, the last blood meal of a fossilised mosquito was said to provide the DNA used to bring back dinosaurs. However, the mosquito they showed in the movie was actually a male giant mosquito, which as you now know doesn’t feed on blood at all!

Queensland Museum's Find out about... is proudly supported by the Thyne Reid Foundation and the Tim Fairfax Family Foundation.