COMMON BENEFICIAL INSECTS
Dr. Leonard Perry, Horticulture Professor Emeritus
University of Vermont
Although we focus on the insects that destroy our landscape
plants and crops, these undesirable insects give a bad name to
virtually all insect species, most of which are beneficial. These
either do no harm, provide food for desirable species such as
birds, or attack and kill the pests we don’t want. Here are ten
common beneficial insects that we should be aware of in our yards
Lady beetles, also known as ladybugs and ladybird beetles, are
perhaps the most well-known beneficial insect. The brightly
colored, rounded beetles are often orange, but can be red, pink or
yellow, and with or without spots. If you see an insect that is
black and orange, with an alligator-like shape, leave it. This is
probably the larva (caterpillar stage) of this beneficial beetle.
Both the larvae and the adults can eat hundreds of aphids in their
lifetimes. They also eat insect eggs, mites, and soft-bodied
insects such as mealybugs.
One of these, known as the multi-colored, Asian, or Halloween
lady beetle, enters homes in large numbers in the fall. They
often then appear in spring in huge numbers in warm indoor areas,
on light-colored surfaces, and on windows seeking to get out.
Proper screening, patching cracks in exterior walls, and just
vacuuming them up are simple controls (I have a hand-vac just for
While lady beetles arguably are the most known predator, spiders
are the most abundant on landscape plants. They’re actually not
an insect, having eight legs and two body parts (insects have six
legs and three body parts), similar to mites and ticks. They are
a diverse group, with over 3,000 species in North America, most
not biting humans.
Ground beetles range in size from a quarter inch to over one inch
long, and are shiny brown, black, or bluish-black. They have long
legs and antennae. Most feed at night on caterpillars such as
armyworms, cutworms, and grubs. They may even eat small snails
and slugs. A pair of adult ground beetles can eat over 300 gypsy
moth caterpillars per year.
Praying mantids also are known by many, being up to three inches
long, with their enlarged front legs held out in front as if
praying. They are not protected by state laws as some believe.
In fact, they may do more harm than good, eating anything they can
including honey bees, other beneficials, and even each other!
Lacewings, both green and brown, are about three-fourths of an inch long as adults, with lacey wings. They are attracted to lights at night, and give off an odor when handled. Larvae are like small alligators, with sickle-shaped mouthparts ("mandibles"). Green lacewing larvae are called “aphid lions” from their large consumption of aphids, as well as mites and other small insects.
Hover flies, also known as syrphid or flower flies, closely
resemble wasps and bees yet they don’t sting. One key difference
is that they have only two wings. Larvae resemble tiny slugs, and
often are found feeding in aphid colonies. Each larva can eat
over 400 aphids. Attract adults with flowers that provide lots of
nectar and pollen.
Predatory bugs feed on nectar and pollen too. They include
several species. Big-eyed bugs are black and white with silvery
wings and bulging eyes. They feed on most insects they can catch,
including chinch bugs, small caterpillars, mites, and insect
eggs. Minute pirate bugs are similar, with similar feeding.
Damsel bugs are under a half-inch long, longer than wide, and with
long legs. They spike on each shoulder. They feed on over 100
types of insects.
Predatory wasps include ones that can sting us, and so we usually
kill them on sight. Bald-faced hornet, yellow jackets, and paper
wasps though, are important predators of caterpillars and similar
soft-bodied insects. For this reason try and coexist with them,
only destroying nests (using proper precautions) if they threaten
people and pets.
Parasitic wasps are a large group of many species, most tiny
(under an eighth inch long, so often overlooked) to an inch and a
half long. They lay eggs inside hosts such as aphids and
caterpillars. Once the larvae hatch, they consume the insect
hosts. Swollen aphids, and caterpillars with white eggs on their
back, are examples of this beneficial insect at work.
Parasitic flies, also known as tachinid flies, are a diverse
group of over 1,300 species. They often resemble, so can be
mistaken for, houseflies, bees, and wasps. Many lay eggs on
hosts, the hatching maggots boring into the hosts and killing them
through feeding. Hosts include caterpillars such as of the gypsy
moth, beetles such as the Japanese, sawfly larvae, true bugs, and
grasshoppers among others.
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