JUNE
2001

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

06-14-01

These Garden Good Guys Don't Wear White Hats

Most gardeners aren't fond of insects. For the most part, gardeners see insects as pests-something to be avoided or killed. And for good reason. Many insects are plant feeders. When some creature feeds on plants tended by a dedicated gardener, sparks are likely to fly.

But not all insects create problems for gardeners. Butterflies, for instance, are generally admired by humans. These flying flowers are actually encouraged by many gardeners. In fact, many gardens include specific plants just to attract butterflies. Some gardens are entirely devoted to plants supportive of butterfly populations.

Other not-so-showy insects also benefit gardeners. These insects are those that make meals out of other insects. Called predators and parasites, these insects help get rid of the pest insects that gardeners hate.

Ladybugs, also sometimes called ladybird beetles, consume aphids as standard fare for breakfast, lunch and dinner. Ladybug children also make meals out of aphids. In this case, ladybugs turn aphids into a family picnic, much to the delight of the gardener.

Aphids are also on the menu of immatures of a group of flies called syrphids. These flies are sometimes called flower flies or hover flies, based on where they can be found and their habit of flying in one place. These flies resemble bees in color and marking and are incorrectly called sweat bees. While the adult flies aren't predators, their kids are.

Another aphid-eater that deserves a tip of the gardener's hat is the lacewing. Lacewings are soft-bodied insects with large membranous wings with lots of crossveins that have the look of lace, hence their common name. Their scientific order name is Neuroptera, meaning nerve wing. Some adults feed on aphids, but their immatures are always vicious predators. These immatures are shaped like alligators, and their voracious appetite supports the name. They are sometimes called aphid lions because of their predatory behavior.

So hungry and ruthless are newly hatched lacewings that they will consume their brothers and sisters if given the chance. So the lacewing mother-to-be wisely places her eggs on a stalk. The stalk is tall enough so that the first hatched cannot reach the egg and make a meal out of its brothers and sisters before they hatch.

Lacewing immatures have sickle-shaped jaws that are hollow tubes. They impale an aphid with those jaws and suck the juices out of the helpless insect. To the cheers, we must assume, of gardeners who can appreciate the death of the plant-pest aphids!

Another insect that makes a living by eating insects is the praying mantid. These not-so-pious carnivores feed on any insect that they can catch. Unfortunately, from the gardeners perspective, the mantids do not distinguish between beneficial and harmful insects. These insects are as likely to consume a honey bee as an armyworm moth. However, gardeners love to have mantids in the garden. They are large insects and easy to see. Alert gardeners may also get to witness a mantid dining on some pest insect. There is a sight that would warm the cockles of any gardener's heart.

Another group of garden beneficials are insects called ground beetles. These beetles are fairly large insects that are black or dark in color. These beetles and their larvae live in the soil or under plant residue. Both the adult and the immature forms of most of these beetles feed on other insects. They especially like to feed on larval insects that live in the soil. A few feed on weed seeds. Either way, gardeners will find them to be beneficial creatures.

There are some true bugs that are also nice to have in the garden. One, the minute pirate bug, is a small black insect with a white chevron pattern on its back. They are fierce predators and feed on all kinds of small arthropods, including aphids, thrips, spider mites and small caterpillars. They have also been known to bite humans when given the chance!

The spined soldier bug is appropriately named. It is shield-shaped and a brownish color. It stabs its prey and sucks out the body fluids. So vicious is this predator that it has been known to devour its own young.

Damsel bugs are also predators. Don't let the name of this brown-colored bug fool you. Both the adult and the immature feed on small insects by sucking the juices from the prey through their curved needle-like beaks.

Hey, it's a bug-eat-bug world out there. The only problem is that gardeners can't tell the good guys from the bad guys by the color of hats that they wear!

 

Writer: Tom Turpin
Editor: Olivia Maddox