Other Pollinators: Mosquitoes


Excerpted from awkward botany

Mosquito - the other pollinator
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. They even play an important role in the food webs found inside the pitchers of northern pitcher plants (Sarracenia spp.). Interestingly enough, Arctic mosquitoes influence the migration patterns of caribou. They emerge in swarms so big and so voracious that they have been said to kill caribou through either blood loss or asphyxiation.

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 Science

Mosquito pollination The scientific literature describes the pollination by mosquitoes of at least two plant species: Platanthera obtusata (syn. Habenaria obtusata) and Silene otites. P. obtusata – bluntleaved 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, pollinia (clusters of pollen) become attached to their eyes and are 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.”

Accidental Pollinators

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

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.

Orchids

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.