11 Ontario insects that are beneficial to your garden

Published: June 2, 2021

Ontario is teeming with insects—the good ones, the bad ones, and the in-betweeners—but they’re all part of the natural balance. Even the mosquitoes and midges that pester us on summer evenings are food for other organisms. Some, however, are standouts—they provide valuable services to gardeners and farmers by eating other, less desirable critters and they help dispose of detritus. And many are remarkably beautiful.

The next time that you plunge your trowel into the soil or embark on a round of weeding, keep an eye out for these beneficial arthropods, and give them the respect they deserve. More than 20 species are at risk or endangered in Ontario.

Beetles

There are more than 8,000 species of beetles (order Coleoptera) that are native to Canada, many of which are found in Ontario. Some of them are viewed as pests, but many are predators of pestilent insects themselves. And some help dispose of decaying animals and plants, returning their carbon to the soil and perpetuating the cycle of life.

Fireflies:

Did you know that fireflies (family Lampyridae) are beetles? Their bioluminescent mating displays light up summer nights on every continent aside from Antarctica. As larvae, they devour pest organisms including snails and slugs. Some adult females may mimic the flashes of other species and eat the males drawn to their signals. And, funnily enough, some species don’t even light up. Of the 29 species of Canadian firefly, 19 are found in Ontario.

Here are some firefly species to look for:

  • Big Dipper firefly (Photinus pyralis)
  • Black firefly (Lucidota atra)
  • Boreal firefly (Pyractomena borealis)
  • Pennsylvania firefly (Photuris pennsylvanica)

Tiger beetles:

Tiger beetles (family Carabidae; subfamily Cicindelinae) live up to their name. They look like the predators they are—athletic, fast, and streamlined—and they prey on all sorts of insects that plague gardeners, from grasshoppers to caterpillars. Many are also beautifully iridescent. Ontario boasts 14 species.

Here are some tiger beetle species to look for:

  • Northern barrens tiger beetle (Cicindela patruela; endangered)
  • Six-spotted tiger beetle (Cicindela sexguttata)
  • Twelve-spotted tiger beetle (Cicindela duodecimguttata)

Rove beetles:

Rove beetles (family Staphylinidae) aren’t the most charming of the Coleoptera. They’re skittery and gross and frankly, look a lot like earwigs. They also produce toxins that can be mildly irritating to human skin, but they more than make up for it by eating a range of pests, from mites to aphids to mealybugs. And as long as you don’t grab or squish one, they’re unlikely to cause you any harm.

Here are a couple of rove beetle species to look for:

  • Large rove beetle (Platydracus maculosus)
  • Gold-and-brown rove beetle (Ontholestes cingulatus)

Soldier beetles:

These relatives (family Cantharidae) of fireflies feed on everything from the eggs of grasshoppers to aphids to pollen and nectar. (Beetles are actually under-appreciated pollinators.) They don’t light up like their glowing relatives though, and they typically come in shades of brown, red, or yellow.

Here are a couple of soldier beetle species to look for:

  • Common red soldier beetle (Rhagonycha fulva; introduced from Europe)
  • Goldenrod soldier beetle (Chauliognathus pensylvanicus)

Carrion beetles:

Carrion beetles aren’t cutethey’re not shiny or sparkly or particularly lovely in any way, but they do get rid of things that are even worse. Most of them feed on decaying animal corpses or on the fly larvae that infest them. Gross? Yes. But for gardeners, this is a good thing. Critters that die amongst the roses are disposed of in short order by these beetles and other organisms. In many cases, you won’t even know their remains were there at all. An estimated eleven species of carrion beetle inhabit Ontario.

Here are a couple of carrion beetle species to look for (or not):

  • American burying beetle (Nicrophorus americanus; this species hasn’t been seen since 1972)
  • Red-lined carrion beetle (Necrodes surimanensis)

Dragonflies and damselflies

The order Odonata consists of the dragonflies and damselflies. Dragonflies are larger and can be distinguished by their unfolded wings, which extend horizontally from their bodies. Damselflies are more delicate, with waifish, slender abdomens and wings that fold along their backs when they are at rest. There are at least 170 species of Odonata native to Ontario. Both of these groups of insects are important predators of flying insect pests as adults. And as larvae, they may help to keep down populations of mosquito larvae and other aquatic nuisances. If you keep a pond, you may find their larvae lurking in the depths. Beware: smaller fish may succumb to their appetites.

Dragonflies:

It’s worth learning about dragonflies just for their names. These jewel-toned fighter pilots have some of the most evocative and original monikers in the insect world.

Here are some dragonflies to look for:

  • Autumn meadowhawk (Sympetrum vicinum)
  • Blue dasher (Pachydiplax longipennis)
  • Common sanddragon (Progomphus obscurus)
  • Common whitetail skimmer (Plathemis lydia)
  • Harpoon clubtail (Gomphus descriptus)
  • Hine’s emerald (Somatochlora hineana; endangered)
  • Pygmy snaketail (Ophiogomphus howei; endangered)
  • Twelve-spotted skimmer (Libellula pulchella)

Damselflies:

These delicate cousins of dragonflies are worth a look too. They tend to sit still for longer, at least in my experience. The ebony jewelwing in particular is a sight to behold…it looks like it belongs in a rainforest with a glistening metallic abdomen and shimmering, emerald-margined wings.

Here are some damselflies to look for:

  • Azure bluet (Enallagma aspersum)
  • Double-striped bluet (Enallagma basidens)
  • Ebony jewelwing (Calopteryx maculata)
  • Rainbow bluet (Enallagma antennatum)

Wasps

Wasps (order Hymenoptera) get a bad rap. A few species do sting, sometimes aggressively, but these relatives of bees and ants are enormously useful in an ecological sense. Some dispose of waste, breaking down rotting fruit and flesh. Others lay their eggs in pest insects, limiting their populations. They also serve as pollinators for many plant species, and the vast majority are completely harmless. Some, in fact, are not much bigger than a pinky nail. Even the scariest ones are usually uninterested in humans.

Here are some wasps to look for:

Ichneumon wasps (family Ichneumonidae):

These solitary species parasitize all sorts of insects, from beetles to moth and butterfly larvae. The giant ichneumon specializes in hunting the pigeon tremex (Tremex columba), a horntail that lays its eggs in dying trees.

  • Giant ichneumon wasp (Megarhyssa macrurus)
  • Coelichneumon species
  • Mesostenus thoracicus

Sphecid wasps (family Sphecidae):

These intimidating but nonaggressive solitary wasps cart off loads of caterpillars, grasshoppers, and crickets to feed their young. Mud daubers create tubes out of soil and stock them with spiders. The structures they create are often found attached to decks and brickwork. With its surreal glossy blue coloration and rapid aerial maneuvers, the steel blue cricket hunter is particularly worth observing.

  • Black and yellow mud dauber (Sceliphron caementarium)
  • Common threadwaisted-wasp (Ammophila procera)
  • Great golden digger (Sphex ichneumoneus)
  • Steel blue cricket hunter (Chlorion aerarium)

Assassin bugs

Assassin bugs (family Reduviidae) are rapacious predators. Like spiders, they inject their quarry with digestive fluids and then eat their liquified insides. Due to their ambush style of predation, they make for easy observation as they crouch motionless on stems and leaves, waiting for something juicy to walk by. Be sure to note the pointy proboscis tucked beneath the body on most species. This is the apparatus they use to drain their prey.

Here are some assassin bugs to look for:

  • Milkweed assassin bug (Zelus longipes)
  • Pale green assassin bug (Zelus luridus)

Mantidflies

They’re neither mantises nor flies. Mantidflies (family Mantispidae) are actually relatives of lacewings, but they do fly and their raptorial forelegs resemble those of the more familiar praying mantis. They use them in the same way too. Both adults and larvae can have a significant effect on insects that might otherwise become pests.

Here are some mantidflies to look for:

  • Four-spotted mantidfly (Dicromantispa interrupta)
  • Wasp mantidfly (Climacellia brunnea)

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