Pollinators, Predators and Parasitoids: an introduction to beneficial insects

You’ve likely heard about the honey bee crisis, colony collapse disorder, and the struggles of beekeepers in recent years. But have you heard about the rapid decline in the populations of other insects?

The Guardian posted an article earlier this month alarmingly titled Plummeting Insect numbers threaten the ‘decline of nature’ , in which the author states that over 40% of insect species are declining and 30% are endangered in North America. A study of insect populations in nature reserves in western Europe found native insect numbers have declined 75% over the past three decades. This disturbing trend seems to be a global phenomenon as studies around the world are presenting similar reports, and we should be paying attention.

These small, overlooked invertebrates are actually the backbone of our ecosystems, keystone species that determine the stability of the whole. They dictate the population health of songbirds, waterfowl, bats, fish, small mammals, and amphibians, which in turn dictate the stability of the higher trophic levels. Bears and other animals with a diet of berries, fruit and seeds will feel the decline of pollinators, as will plant species that depend on pollinated seed for dispersal. Seventy five percent of our food crops require insects and other beneficials for pollination. As much as humans like to think we are somehow removed from nature, we directly impact, participate in, and are dependent on our surrounding ecosystems. The health of these small beings will affect our own well being in the long run.

While there are some bigger global issues contributing to their collapse, such as habitat loss, neonicotinoids, pesticide use, agricultural practices, climate change, and mismanagement of wild spaces, there are actions that can be taken on the local level to encourage and support native beneficial insect populations. The first step is knowing what they are and what they do in our home environments. Insects are invaluable players in the functioning of our forests, farms, and gardens, performing more services in pest control, pollination, carbon sequestration, soil aeration, and nutrient cycling than we can comprehend.

The Pollinators

Honey bees are great – we eat a lot of honey in our family and really value having beekeeping friends and neighbours nearby. But the honey bee has become the poster child for pollination, which isn’t exactly a title they should have. The European honey bee, Apis mellifera, is actually an introduced insect not native to North America. While we currently depend on them for pollination of the majority of our crops, that is mainly because we have set up agricultural systems that are devoid of habitat for native pollinators, so we have to artificially create that habitat and import pollinators to do the job. The problem is, if honey bees collapse, three quarters of our food supply could too. It’s a fragile system that could potentially fail, unless we begin changing the way we farm and garden to strengthen their populations and intentionally use the services of native pollinators.

clockwise from top left: Monarch butterflies, orchard mason bees, syrphid flies, and bumble bees are just a few of the native pollinators in our region

There are too many types of native bees in BC (over 400!) to list here, but if you want to get to know them better, the Master Gardener’s of BC site has a list of southern BC bee species worth checking out. There are 35 species of bumble bees in BC alone; their ample hair, tendency to linger longer on each flower, and ability to fly in cooler weather makes them more effective and efficient at transferring pollen between flowers than the honey bee.

Pollinators include far more than just bees. Butterflies, syrphid (hover) flies, day-flying moths, lacewings, wasps, hornets, hummingbirds, and flower beetles are all vital in the garden for pollinating flowers and food crops. The Environmental Youth Alliance has a great pollinator photo guide that gives a good overview of commonly seen BC pollinators.

Predators

Ladybugs, ground beetles, predatory mites, and spiders are all predators of pest insects

Most insects don’t just eat pollen and nectar. Many eat other insects. The difference between a pest insect and a beneficial insect is a bit of a blurry line. Pest insects are just those that like to eat the same thing we do, and compete with us for our food supply. Beneficial predatory insects are playing on our team, indirectly defending our food source by eating our competitors. The goal in ecological gardening or farming is to create space for a diversity of insects so that there is always a predator species nearby to prevent minor levels of pests from turning into crop-destroying infestations.

Ladybugs are probably the most familiar predator – gardeners are known to purchase them for their ability to eat aphids, only to find they fly away to eat the aphids in a neighbour’s yard. Predatory beetles will feed on caterpillars, slugs, snails, grasshopper eggs, and other soft-bodied insects. Some ground beetles are known to actually kill more prey than they can consume. Predatory mites consume aphids, thrips, other mites, scales, and insect eggs. Spiders and praying mantis will eat anything they can find and are great generalists. Stink bugs, big-eyed bugs, minute pirate bugs, and damsel bugs have a diet of pollen and nectar as well as range of pest insects and larvae. Yellow jackets, bald-faced hornets, and paper wasps will prey on caterpillars and soft-bodied insects. Lacewings are also known as “aphid lions” for their ability to decimate aphid populations as well as other small insects.

Parasitoids

There’s a whole other category reserved for beneficial insects that don’t directly consume other pest insects, but lay their eggs on other insects and as those eggs hatch, the larvae consume their host. The parasitoid category includes parasitic wasps, rove beetles, and tachenid flies. These insects often eat pollen and nectar as their main food source and need undisturbed habitat throughout their life cycle in you want them to stay in your garden.
Parasitic wasps, rove beetles, and tachenid flies will lay their eggs on other insects, such as this tomato hornworm. Those eggs will hatch and consumer their host.

There are many insects and soil organisms that don’t fit in these categories, and yet are incredibly beneficial. Ants make the cut for their ability to tunnel and aerate the soil, sequester carbon, process waste plant material, and prey on other insects. Earthworms and other soil organisms are constantly working and managing our soil systems and are extraordinarily beneficial, but that opens whole other topic for some other day…

Welcoming the Beneficials

I used to walk past wildflowers or a garden bed of buckwheat and clover in bloom and think that all the buzz and activity was just a bunch of honey bees doing their business. But as I am learning more about the diversity of insects out there and their incredible ecological services, I am noticing how there are often dozens of species busily at work pollinating and predating on pests. While I can’t control what is happening to insects on a global level, I can control how much habitat and food these organisms have in my own garden and orchard.

In the next post on this blog, 5 Ways to Garden for Beneficial Insects, I’ll cover a few simple ways we can make our landscapes, gardens, and farms more welcoming towards native beneficial insects. The next entry will also cover some of the best insectary flowers to plant that support healthy native insect populations in this region, as well as bring more beauty and diversity to our gardens. If you  would like additional reading, there are some great resources listed below.

If you have questions, comments, or observations about beneficial insects in your life, please feel free to comment below!

Some great resources on native benefical insects put out by the Xerces Society. Available for ordering online or at your local library via interlibrary connect.
Resources and Good Reads:

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