Other Pollinators — Mosquitoes
Excerpted from awkward botany
It is difficult to have positive feelings about mosquitoes, especially during summer months when they are out in
droves and our exposed skin – soft, supple, and largely hair-free – is irresistible to them.
We are viewed as walking blood meals by female mosquitoes who are simply trying to produce young
– to perpetuate their species just like any other species endeavors to do.
Unfortunately, we are left with small, annoying bumps in our skin –
red, itchy, and painful – risking the possibility that the mosquitoes that just drew our blood may have passed
along any number of mosquito-borne diseases, some (such as malaria) that potentially kill millions of people
every year. For this, it is okay to hate mosquitoes and to long for the day of their complete eradication from the
planet. However, their ecological roles (and yes, they do have some) are also worth considering.
Male mosquitoes never bite and females need the protein in blood only to produce
eggs, so the normal food of adult mosquitoes is actually nectar from plants.
There are more than 3,500 species of mosquito. Luckily, only 200 or so consume human blood. Mosquitoes go
back at least 100 million years and have co-evolved with species of plants and animals found in diverse habitats
around the world. Adult mosquitoes and their larvae (which live in standing water) provide food for a wide variety
of creatures including birds, bats, insects, spiders, fish, frogs, lizards, and salamanders. Mosquito larvae also
help break down organic matter in the bodies of water they inhabit.
However, blood is not the main food source of mosquitoes; flower nectar is. Males don’t consume blood at all,
and females only consume it when they are producing eggs. Any insect that visits flowers for nectar has the
potential to unwittingly collect pollen and transfer it to a nearby flower, thereby aiding in pollination. Mosquitoes
are no exception. They have been observed acting as pollinators for a handful of species, and could be acting as
pollinators for many more.
The scientific literature describes the pollination by mosquitoes of at least two plant species: Platanthera obtusata
and Silene otites.
P. obtusata, the blunt-leaved orchid, is found in cold, wet regions in
North America and northern Eurasia. It is pollinated by mosquitoes from multiple genera including several species
in the genus Aedes. Mosquitoes visit the flowers to feed on the nectar and, subsequently, pollen
become attached to their eyes and is moved from flower to flower. This scenario likely plays out in other
species of Arctic orchids as well*.
Despite the list of functions that mosquitoes serve in their varied habitats, an article that appeared in Nature back
in 2010 argues for wiping mosquitoes off the Earth, stating that “the ecological scar left by a missing mosquito
would heal quickly as the niche was filled by other organisms.” And even though “thousands of plant species
would lose a group of pollinators,” mosquitoes are not important pollinators of the “crops on which humans
depend,” nor do they appear to be the sole pollinator of any single plant species [the species mentioned above
are pollinated by other insects as well]. Eliminating mosquitoes, however, is more of a pipe dream than a realistic
possibility as our “best efforts can’t seriously threaten an insect with few redeeming features.”
Mosquitoes are also believed to be accidental pollinators of many plants in the family Umbelliferae. These plants
can be pollinated by nearly any insect that walks across them seeking nectar. Garden variety members of the
family thought to be pollinated by mosquitoes include anise, caraway, carrots, celery, coriander, cumin, dill and
parsnips. The umbrella-shaped flowers are easy food sources for a wide range of insects.
Goldenrod uses mosquitoes, as well as other insects, for pollination. You might think it appropriate that an
annoying insect would help pollinate a flower notorious for causing hay-fever, but scientists believe that goldenrod
really isn't responsible for fall allergies, compared to other less noticeable plants that bloom at the same time, but
which have smaller grains of pollen that blow in the wind.
The sticky grains of goldenrod pollen adhere to mosquitoes and other insects as they forage over the blooms.
Mosquitoes have been studied as pollinators of the blunt bog orchid (Habenaria obtusata or Platanthera obtusata),
which is a small-flowered orchid of little commercial significance. This plant dwells in the conifer swamps of the
northwest United States, where mosquitoes are abundant. A similar swamp orchid, early coral-root (Corallorhiza
trifida), is also thought to be pollinated by mosquitoes, but no studies currently confirm this theory.
Studies of caged mosquitoes demonstrate that these pests are purposeful about their nectar feeding, with the
male mosquitoes using their long proboscis to probe for the nectar spurs. Upon locating a spur, the mosquito is
forced to press one of its compound eyes against a pollinarium to reach the nectar. When withdrawing from the
flower, the mosquito has pollen grains stuck to the eye. These grains force the mosquito to probe the nectary near
the style of the next plant, depositing the grain of pollen on the sticky female structure.