A Summary of Beneficial Insects in Your Garden
Cathy Kavassalis – Halton Master Gardener
(Originally posted on the Facebook Page for Master Gardeners of Ontario)
We often focus on insect pests in the garden, like aphids. In this post, I would like to introduce you to some of our fierce garden helpers, like Tiger Beetles, Antlions and Dragonflies. Yesterday, my son messaged me a photo of a beetle devouring aphids in his garden then sprinting off in search of more food. This is the beautiful metallic green, six spotted tiger beetle, Cicindela sexguttata (sometimes they have more than six spots). It is one of hundreds of predatory insects that can help reduce pests in your garden.
Get to know these beneficial insects and encourage them to live and breed in your garden.
The six-spotted tiger beetle is one of many species of ground beetles that you might find in your yard. Steve Marshall from University of Guelph has created a page on TIGER BEETLES OF ONTARIO if you want to see other varieties. Some, like the endangered Northern Barrens Tiger Beetle, you are unlikely ever to encounter. They are all voracious eaters.
Tiger beetles have big eyes and their great eyesight helps them spot just about anything that moves. “They eat a wide variety of pest organisms including aphids, moth larvae (such as army- worm, cutworm and gypsy moth larvae), beetle larvae (such as the corn rootworm, Colorado potato beetle and the cucumber beetle), mites, and springtails. They have also been used effectively to control slugs in greenhouses.” (Entomological Notes PennState – “Ground and Tiger Beetles,” ). Not only are the adult tigers great predators, but also their larvae can reduce pests in your soil. Tiger beetle larvae dig burrows in the ground (sometimes quite deep) and from there, they ambush prey. (Here’s a great page on their Biology, Life Cycle, & Behavior from entomologists at the University of Nebraska). Like antlions, they prefer bare ground (no mulch), though they are not confined to sandy soils (my son’s garden is clay-loam).
To support tiger beetles and antlions, leave access to soil and don’t use pesticides. (I also recommend NOT using entomopathogenic nematodes, like Heterorhabditis bacteriophora or Steinernema carpocapsae, as these can have non-target impacts … Here are some interesting observations on ground beetles avoiding nematode infected arthropods).
If pests are a problem, these beetles are a solution. So are antlions. Antlions belong to a group of insects called Neuroptera or netwinged insects. They are more specifically in a family of netwings called Myrmeleontidae (which means ant-lion in Greek). The adults are rarely seen, but the pitfall traps built by larvae may be easier to spot. These insects prefer dry, sandy soils sheltered from rain to build their cones of death. What do they eat? Well, many small arthropods, but ants are a particular favourite. (Here’s a Youtube video showing how effective they can be).
Lacewing larvae (Ant Lion) and adult Lacewing (to right)
Some species are predators as adults; others feed on pollen and nectar. Though ferocious in appearance, they will not bite unless really provoked (my sister keeps them as pets). There are several closely related beneficial insects, you might like to get to know: Ascalaphidae (the owlflies), Chrysopidae (the green lacewings seen in cover photo above this article), Hemerobiidae (the brown lacewings), Mantispidae (the mantisflies) Learn more here: www.knowyourinsects.org )
So lions and tigers – YES! but dragons? Perhaps, one of the most fearsome of aerial hunters is the dragonfly. On Nature Magazine has a fantastic guide to the Dragonfly and Damselfly of Ontario, collectively called Odonata. For those of you near water, or with a backyard pond, encourage dragon and damselflies to nest or hunt in your yard. (Check out this video of dragonflies hunting from Harvard University). Their larvae will help keep mosquitoes out of your ponds and reduce pests in your garden. Support them by providing a range of native plants in and around your ponds. Visit the website of your local conservation area to find out about native plants for your region.
Dragonfly & Damselfly