When we think of pollinators, most people only consider the work of honey bees and butterflies. To mark this year’s Pollinator Week (June 17-23), let’s delve more deeply into the vast and varied pollinator ecosystem.
While the European Honey Bee (Apis mellifera) is the bee and pollinator most people are most familiar with, it’s important to remember that this is a non-native livestock species in North America, specifically brought here to pollinate non-native crop plants and produce honey and other bee products for human usage.
75% of native plants to North America require an insect (most often a bee) for pollination. There are 4,000 native bees that co-evolved with our native plants to affect that pollination for millennia before the introduction of Honey Bees. As there are many crop species native to the Americas (squash, pumpkins, sunflowers, cotton, etc.), there are likewise many native bees that are obligate specialists for pollinating these species. That said, even in non-native crops native bees can often be either the primary pollinator or significantly supplement Honeybee pollination. Unlike honeybees, most of our native bees are solitary and either nest underground or in dead wood/plant stems.
While bees tend to be the most effective pollinators, many other insects perform important (if sometimes accidental) pollinator roles. Unlike bees, wasps do not purposefully collect pollen. However, they are avid nectar drinkers. Despite being less hairy than bees, they do inadvertently transfer pollen from plant to plant during nectar collection, and (largely based on the sheer number of them doing this) have an appreciable impact on overall plant pollination.
Surprisingly, flies are the second most important pollinators after bees—especially in high altitude/latitude environments where bee diversity is lower, or in early spring when cooler temps mean bees are less active. Flies collect nectar and pollen as food, but unlike bees they don’t actively collect pollen to bring back to their young, so they are passive (but effective) pollinators.
Some plants like Skunk Cabbage (Symplocarpus foetidus) or Paw paw (Asimina triloba) have evolved to actively attract flies by having flowers that look and smell like rotting meat. This attracts flies who want to lay their eggs on carrion. While the flies are searching for the meat (which is nowhere to be found) they buzz around inside the flowers and pass pollen from one plant to the next. Interestingly, most of these flies are defenseless but many of them have evolved to look like stinging wasps and bees to deter predators from trying to eat them.
Beetles play an active role in pollination as well, and in fact beetles were one of the first groups of insects to begin pollinating flowers. As a result, some of the more ancient lineages of plants like Magnolias tend to be beetle pollinated. Beetles visit flowers to eat pollen and other flower parts, but in doing so they often get covered in pollen themselves and transfer that pollen to other plants, becoming messy, accidental, but effective pollinators.
Butterflies and moths are also accidental pollinators. Some, like hawkmoths, do almost no pollination as their long tongues often allow them to access nectar without touching any other flower parts. Others, like Yucca moths, are essential pollinators for their host plants. Most are middling pollinators that provide some accidental pollination as they flit from flower to flower collecting nectar.
The real ecological benefit these insects provide is in the form of their offspring. Butterflies (and overwhelmingly) moths produce copious amounts of caterpillars which are essentially living tubes of nutrient rich goo essential to the life cycles of animals at all trophic levels. They are particularly important to songbirds as food for their offspring, so it is crucial to provide food host plants for caterpillars.
Some species are generalists and can eat the foliage of numerous species of plants. However, many—most famously the Monarch—only have one family, genus, or species that acts as their host plant. As a result, supporting those plants is essential in helping those particular butterflies and moths to thrive. Scorned for its rash-causing oils, Poison Ivy (Toxicodendron radicans) is the obligate host for the Eyed Paectes Moth, proving that even plants thought of as undesirable weeds from a human perspective play an important, if often unseen and unacknowledged role in ecosystem services.
Vertebrates like birds, bats, marsupials, and many other types of larger animals play a role in pollination around the world. In the northeastern US, the best known and best-loved example of one of these animals is the Ruby-throated Hummingbird (Archilochus colubris). Hummingbirds are also accidental pollinators who transfer pollen from flower to flower in search of nectar. Famously, they prefer tube shaped red or orange flowers like Cardinal flower (Lobelia cardinalis), Beebalm (Monarda didyma), or Trumpet Honeysuckle (Lonicera sempervirens) but they will drink nectar from a wide range of flowering plants including Autumn Olive (Elaeagnus umbellate), Tulips (Tulipa sp.), and Tuliptrees (Liriodendron tulipifera).
Happy Pollinator Week 2024–let’s commit to supporting and appreciating the work of these important creatures in every way we can!