Lady beetles or ladybird beetles are very familiar and widely recognized predators of garden pests. Their phylum is Arthropoda, Class: Insecta; Order: Coleoptera; and Family: Coccinellidae. True bugs have sucking mouth parts, to extract juices from plants, but lady beetles, being predators, have chewing apparatus, so are not classified as bugs. They feed on soft-bodied insects such as aphids, spider mites, small caterpillars and insect eggs. Adults may eat pollen and nectar. Some are specialists, such as Twice Stabbed lady beetleS, ( 2 red spots on black) which feed exclusively on scales.
Lady beetles undergo complete metamorphosis, beginning life as a tiny egg, laid on a plant, usually near a food source. The larvae hatch within 3 to 10 days, depending on ambient temperature and they begin to eat almost at once. Larvae have 4 instar phases and are voracious consumers of aphids and such at all stages, so are very beneficial to gardens and crops. The larvae do not resemble the adults at all, looking like tiny alligators, with elongated bodies and bumpy exoskeletons. They may have spines or a waxy coating which makes them resemble mould or mildew.
After 2 to 3 weeks, the larvae pupate, attached to a plant. The adult beetle emerges 1 to 2 weeks later in its familiar dome-shaped form, with wings beneath its hard spotted elytra – wing covers. Adult lady beetles overwinter in your garden when you provide suitable habitat. They form aggregates, or clusters under leaves, stones and mulch, emerging in spring to mate. Depending on the species, females may lay up to 1000 eggs in their lifetime.
When threatened, ladybugs “reflex bleed,” releasing haemolymph from their leg joints. The yellow haemolymph is both toxic and foul-smelling, and effectively deters predators. The lady beetle’s bright colours may signal its toxicity to predators as well.
There are thousands of species of lady beetles world-wide. They inhabit different niches and are a variety of colours and patterns. Unfortunately, their numbers are in decline due to the same problems all insects face: loss of habitat, over-use of pesticides, light pollution, climate change and being pushed out by alien species.
Some alien species of lady beetles in Canada: Multicoloured Asian lady beetles, were brought to North America in the 1970s to control aphids and other crop-eating insects. “Their fast reproduction and ability to withstand fairly harsh winters have helped them become one of the main species in Canada.” (“Ladybugs – Canada.ca”) They are slightly larger than native species, usually 6 to 10 mm long (.24 to .39 inches). They range in colour from a mustard yellow to a dark reddish orange. They have a varying number of black spots on their wing covers, and some may not have any spots.
They become problematical when they seek to overwinter indoors. Unlike native species, they would much rather be in your home during winter rather than under the leaves outside.
Seven-spotted Lady Beetles were introduced from Europe, again to control aphids. Fourteen- spotted lady beetles are yellow to orange, with rectangular spots. They were brought in to control Russian wheat aphids. Alien lady beetles are effective consumers of pests.
On the other hand, Canada has many native species of lady beetle. Convergent have up to 13 spots. Pink-spotted are somewhat elongated and are generalists which eat mites, insect eggs, nectar, water, pollen, and eggs of the moths which destroy corn crops. The Twenty-spotted lady beetle is cream coloured with brown spots and loves to much mildew and fungus. Two-spotted lady beetles do, indeed have 2 spots.
The Thirteen-spotted lady beetle is a northern species, found in wet meadows, marshes, flood plains and lakeshores.
The Eye-spotted lady beetle lives in the canopy of coniferous forests, munching aphids and other delectable pests.
The convergent lady beetle is among the most common lady beetle species throughout North America and is an important natural enemy of aphids, scales, thrips, and other soft-bodied insects. It will also feed on pollen and nectar from flowers when prey is scarce. This species can be found in habitats ranging from grasslands, forests, agricultural fields, and gardens. It is one of the lady beetles that are collected from mass aggregations for distribution to the pest control industry. Purchasing lady beetles for your garden is pretty much a waste of money since they are gathered while hibernating. Their instinct when they emerge from hibernation is to fly away in search of food. In an enclosed environment such as a greenhouse, however, lady beetles can be very useful.
The Three-banded and Transverse lady beetles are endangered in our area.
For more information about lady beetles, head out to your garden this spring. In the meantime, you can consult The Vermont Atlas of Life: val.vtecostudies.org/projects/lady-beetle-atlas/ to learn more about lady beetles than you can imagine.
Submitted by Leslye Glover, Master Gardener