Bugs, flies and beetles are all around us. Many people think
of all insects as pests without knowing that many of them are garden friendly
or beneficial insects. These beneficial insects each play an important role in
our environment.
Is there really such a thing as a good bug? Obviously!
Unlike Humans, Mother Nature has kept everything balanced in the environment. A
nice bug does no harm; rather it will control those insects which eat any of
your plants or crops. A really good bug eats those insects that destroy your
plants or crops. Some of these insects help the gardener by pollinating
flowers, while predatory insects eat other pest insects. There are other
insects that break down decaying matter, helping to build good soil.
We never tend to appreciate the insects, forget about their
lifecycles. We just want to get rid of them all. But they have a very important
role to play in the Environment. Even the most avid gardeners may not be
interested in the reproductive cycles of the green lacewing, but when they
realize that one prolific female lacewing could be responsible for wiping out
40,000 pests each season, they can’t close their wide open mouth!
Attracting these “garden friendly” insects and be greatly
beneficial to your garden, thus the reason they are called beneficial insects.
Protect your beneficial insects by avoiding toxic sprays/dusts.
Below is a list of the top beneficial insects and what they
do to help. Most insect problems can be biologically controlled with these
insects…
Parasitic wasps – Ranging from tiny Trichogramma wasps to huge ichneumonid wasps, parasitic wasps inject their eggs into pest insects. The larvae hatch and grow by absorbing nourishment through their skins, eventually killing the host insect.
Many of the solitary wasps are parasitoidal, meaning that they raise their young by laying eggs on or in the larvae of other insects. The wasp larvae eat the host larvae, eventually killing them. Solitary wasps parasitize almost every pest insect, making wasps valuable in horticulture for biological pest control of species such as whitefly in tomatoes and other crops.
Bee Flies - These are family of flies, some of which are really beautiful to see. the adults feed mainly on nectar and pollen, acting as important pollinators, while their larvae generally are predators or parasitoids of eggs & larvae of other insects.
Braconid Wasp - Braconid wasps have such a strong reputation as killers of pests that they are widely used in agriculture. A few adults prey on other adult insects, but most feed on pollen. It's the larvae that are extremely valuable controls of garden, farm and forest pests. Egg and larval stages of various braconid wasp species chow down on larvae, pupae or nymphs of numerous pest moths, aphids, beetles, flies, ants or other bugs.
Yellow Jackets and Hornets - Although feared by many people, these insects are actually wonderful pest predators. They dive into foliage and carry off insects that are damaging your plants to feed their brood. Potter wasp is one the examples of solitary predator.
Lady beetles – A favorite with home gardeners, ladybugs are
the best known beneficial insects around. There are more than 3,000 species of
these small to medium sized beetles. Both adults and larvae eat thousands of
pests, feeding on small insects such as aphids, mealy bugs, and spider mites.
Also favored are corn flies, soft scales, whitefly and a wide variety of other
soft-bodied, plant-eating insects. 
Ground beetles – Why they're good: A pest killer in two
stages of its lifecycle, this beetle enjoys snails, slugs, cutworms, gypsy moth
larvae, root maggots, tent caterpillars, Colorado potato beetle larvae and
other pests that spend a stage of their lifecycle in the soil. Larvae feed on
other ground larvae and insect eggs; one grub can eat at least 50 caterpillars. These medium to large, blue-black beetles hide under stones
and logs/boards during the day. At night they prey on cutworms, cabbage root
maggots, snails/slugs and their eggs. Some ground beetles will even climb trees
and feed on armyworms or tent caterpillars.
Rove beetles – These small to medium beetles look like
earwigs without pincers. Many of this species help in decomposing manure and
plant material, while others prey on root maggots.
Syrphid flies – Also called flower or hover flies. Imagine a
pest-killing machine devouring enormous numbers of aphids, up to 400 during
this stage. these black and yellow or
black and white striped flies are commonly mistaken for bees. Laying their eggs
in aphid colonies; the larvae then feed on the aphids.
Tachinid flies – Large, dark grey flies that place their
eggs and larvae on cutworms, caterpillers, stinkbugs, and other pest insects. Tachinid
flies are also natural suppressors of armyworm or tent caterpillar outbreaks.
Dragonflies – Along with the smaller Damselflies,
dragonflies feed on mosquitoes, gnats, and midges, filling their mouths with
prey as they zig-zag around the garden. As adults, dragonflies eat other
insects and can consume hundreds of mosquitoes in one day! They are valued as
predators, since they help control populations of harmful insects. Dragonflies
are usually found around lakes, ponds, streams and wetlands because their
larvae, known as "nymphs", are aquatic. Adult dragonflies do not bite
or sting humans.
Firefly larvae are predators of various insects, slugs, and
snails.
Lacewings - As with most garden "police" insects,
the lifecycle is the secret and the law enforcement is all in the larval stage.
Larvae, often called "aphid lions," are among the most efficient
predators of aphids. They also prey on the eggs and immature stages of small,
soft-bodied insects such as mealybugs, thrips, spider mites and leaf-hoppers.
The larvae, which resembles a tiny alligator, feed on small
insects including aphids, scale insects, and corn flies.
Spiders and Mites – Although they are not really insects,
spiders are some of the best pest predators around, feeding on the larger pest
insects. Predatory mites, also arachnids, feed on plant-feeding mites, such as
spider mites, rust mites, and cyclamen mites. Some will also feed on aphids and
corn flies, while other soil-dwelling mites eat insect eggs, fungus gnat
larvae, or decaying organic material.
Scarab Beetles - Many scarabs are scavengers that recycle
dung, carrion, or decaying plant material. Most of these beetles are nocturnal; except for the Flower Chafers and many Leaf Chafers, which are active during the day. 
The name "Robber flies" reflects their notoriously aggressive predatory habits; they feed mainly or exclusively on other insects and as a rule they wait in ambush and catch their prey in flight. feed on small arthropods, mainly insects.
Beneficial Nematodes are microscopic, non-segmented roundworms
that naturally occur in soil and are used to control soil pest insects. They
only attack soil dwelling insects without exposing plants, earthworms, humans
or animals to any health or environmental risks. Thus totally a safe biological
control in pest insects. Inside the nematode's gut is the real weapon..symbiotic
bacteria that when released inside an insect kill it within 24 to 48 hours.
Most of the wild creatures need a natural habitat to
accomplish their work. Although many of these areas have been reduced in the
past, recently more are being restored to attract the creatures back. Each of
us can help to restore habitats even if we don’t completely understand how
ecosystems work and cannot fully return an area to its wild state. Planting Nirgudi
(Vitex Nigundo) for butterflies, providing organic growing conditions for
plants that bees visit for pollen and nectar, choosing garden plants that are
first and foremost beneficial to wildlife (not primarily because they are
beautiful), helping to keep an existing patch of forest from being destroyed to develop
more concrete buildings, are within the capacity of most of us...