Toxorhynchites sp., the elephant mosquito (Diptera: Culicidae: Culicinae: Toxorhynchitini)
Toxorhynchites is a mosquito genus of 90 species found on all continents except Antarctica. They are the largest mosquitoes, adults reaching 18 mm in length but fortunately they are not blood-feeding, in contrast to most mosquito species. The common name is elephant mosquito, probably referring to their large size and their proboscis which crudely resembles an elephant’s trunk. The scientific name comes from the Greek (toxo; a bow) referring to the similarly curved shape of both the Toxorhynchites proboscis and a bow [as in bow and arrow] and rhyngchos, a snout. The genus has been split into 4 subgenera, two of which, Toxorhynchites and Afrorhynchus, occur in Africa.
The larvae of all Toxorhynchites species develop in the water of natural container habitats such as treeholes. They will also use artificial containers, e.g. discarded automobile tyres. Their developmental strategy is more or less the reverse of their cousins, the biting mosquitoes. Toxorhynchites larvae are predaceous and while the larvae of many species of biting mosquitoes also develop within natural and artificial containers, they are harmless detritovores, using their mandibles to sweep up their food (bacteria, suspended particles etc.) on and under the water surface. Adults, of course, are another story. They are small, several times smaller than Toxorhynchites adults. But size isn’t everything. These small mosquitoes include the feared hematophagous (blood-feeding) flying syringes buzzing around our heads mostly in the late afternoon and early evenings. These include Aedes aegypti, Aedes simpsoni, and Aedes albopictus, vectors of Yellow fever, Dengue, and Chikungunya viruses. In contrast, although they look fearsome, adult Toxorhynchites do not require a bloodmeal, and use their long, curved proboscis solely to imbibe nectar and other liquid sources available in the forest. When ovipositing, females hover above the water surface while "shooting” one or two eggs onto it. Toxorhynchites are autogenous, storing all the essential nutrients to mature their eggs while still larvae. And what larvae! They are ferocious carnivores capturing and tearing apart the unlucky cohabitants with which they share a home, including the defenceless larvae of Aedes mosquitoes. For that reason, efforts have been made to use Toxorhynchites in the biological control of medically important container-breeding mosquitoes by colonizing and mass-rearing Toxorhynchites and releasing adults into the wild. However, these efforts have been met with only moderate success, due mainly to the difficulties encountered in mass rearing this formidable predator.
Credits: Dr Robert Copeland