INSECTS ARE OUR FRIENDS
Most insects and other arthropods found in the yard and garden do not feed on or
harm plants. Many of these are just “passing through” or have very innocuous
habits. Others feed on and destroy pest species. In many cases, the activities
of these beneficial species can completely prevent or greatly limit pest
problems. It is important to recognize these beneficial arthropods so that they
may be appreciated and conserved.
Beneficial arthropods are categorized broadly as either insect predators or
parasites. During development, in both adult and immature stages, insect
predators actively search out and consume several prey insects. Predators
include ladybird beetles, lacewings and spiders. Insect parasites develop in or
on a single host form eggs or larvae deposited by the adult parasite. Common
insect parasites are tachinid flies and the brconid and ichneumonid wasps.
Ladybird beetles – Often called “ladybugs”, ladybird beetles are the most
familiar insect predator. Most adult ladybird beetles are round-oval in shape,
brightly colored and often spotted. The immature or larvae stages, however,
appear very different and often are overlooked or misidentified. Ladybird
beetles larvae are elongated, usually dark colored and flecked with orange or
yellow. Adult and larval ladybird beetles feed on large numbers of small soft-
bodied insects such as aphids. One group of very small black ladybird beetles
(Stethorus) is also very important in controlling spider mites. Ladybird beetles
can rapidly control many developing insect problems, particularly if
temperatures are warm.
Green lacewings – Several green lacewing species commonly are found in gardens.
The adult stage is familiar to most gardeners – a pale green insect with large,
clear, highly-veined wings that are over the body when at rest. Adult green
lacewings primarily feed on nectar and other fluids, but some species also
consume a few small insects.
Green lacewings lay a distinctive stalked egg. Lacewing larvae emerge in four to
then days. These larvae, sometimes called aphid lions, are voracious predators
capable of feeding on small caterpillars and beetles as well as aphids and other
insects. In general shape and size, lacewing larvae are superficially similar to
ladybird beetle larvae. However, immature lacewings usually are light brown and
have a large pair of hooked jaws sticking out from the front of the head.
Syrphid flies – These flies are called by several names such as flower flies or
hover flies. Most are brightly colored, yellow or orange and black, and may
resemble bees or yellow jacket wasps. However, syrphid flied are harmless to
humans. Usually they can be seen feeding on flowers. It is the larval stage of
the syrphid fly that is an insect predator. Variously colored, the tapered
“maggots” crawl over foliage and daily can feed on dozens of small, soft-bodied
insects. Syrphid flies are particularly important in controlling aphid
infestations early in the season when cooler temperatures may inhibit other
Similar in appearance to the syphid fly larvae is a small, bright orange
predatory midge (Aphidoletes). These insects often can be seen feeding within
aphid colonies late in the season.