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Can insects protect my garden ecosystem better than chemicals?

by Jan Phipps, Edgar County Master Gardener

There are many beneficial insects in the garden that prey on other insects.  Several great names indicate their function: robber flies, ambush bugs, and assassin bugs.  The following are a few of the predatory insects with which you want to share your landscape.

Dragonflies are not only beautiful, graceful fliers; they are very efficient predators.  They have a mid-air catch rate of 95%.  How many deer hunters can claim that statistic?

Hoverflies have several aliases: flower fly, syrphid fly, and, erroneously, sweat bees because of their black and yellow stripes.  The adult form spends its days distributing the pollen from flower to flower.  The larval form is the predator, feeding on soft-bodied insects like aphids and scales.
Some Lacewings are predatory in both the adult and larval stages.  They are called aphid lions because of their appetite for aphids.  According to Danae Wolfe, garden writer for The American Gardener magazine, they also eat mealybugs, psyllids, thrips, mites, whiteflies, and even small caterpillars.
Robber flies do not discriminate between beneficial and harmful prey.  They feed on wasps, bees, dragonflies, flies, leafhoppers, butterflies, and even grasshoppers.  They excel in fast aerial chases, returning to a sunny perch to devour their catch.
Ambush bugs are small but mighty, attacking prey that is ten times larger.  They have piercing, sucking mouthparts and raptorial forelegs.  They grab the prey with their forelegs and stab them with their mouth.  Ambush bugs eat various insects, including wasps, butterflies, and bees.
Assassin bugs are dangerous both as nymphs and adults.  They catch their prey like ambush bugs but inject enzymes to start digestion.  They prey on small and medium-sized insects, including caterpillars, aphids, stink bugs, and flies.
Finally, there are the Mantidflies.  According to Wolfe, they resemble a mix between a praying mantis, a wasp, and a lacewing.  They are small and medium-sized predators.  The larval stage feeds on spider eggs.
Why do we care about predatory insects?  With a balance between predators and prey, your garden ecosystem can maintain itself without the need for chemicals.  The best way to do that is to grow a diversity of plants that support all the life cycles of insects.  It is a bug-eat-bug world, but that is a good thing.
Do you have an unidentifiable insect in your garden?  Give the Illinois Extension Master Gardeners of Edgar County a call at 217-465-8585.