With Australia being home to about 500 species of ladybird beetles, it is essential that we know the good, the bad and the beautiful!
Ladybird beetles have been revered across many continents and cultures for centuries, largely due to their symbolism of prosperity, protection and luck. European legends and folklore abound, from being good luck if a ladybird beetle flies into your bedroom, bad luck if you kill one, and a sign of impending marriage if a ladybird beetle crawls across a young woman’s hand!
Medicinal benefits were also espoused, including a cure for toothache. A beetle or two was crushed and rubbed into the tooth cavity. I don’t recommend it. The yellowish fluid secreted by ladybird beetles contains alkaloid compounds that have a foul odour, being a defensive mechanism to ward off predators.
Ladybird beetles make up the beetle family, Coccinellidae. In the U.S., these insects are known as ladybugs, but Diggers members know that ladybirds are beetles and not bugs! The name ladybird has a Christian origin. In medieval Britain, the beetles were known as ‘Our Lady’s birds’ or ‘Lady beetles’. The names were probably inspired by early images of the Virgin Mary wearing a red cloak. Coincidentally, the family name Coccinellidae has its origins in the Latin word coccinus, meaning ‘scarlet’.
The brilliant colours and dark spots of common species of ladybird beetles make them highly visible garden insects. The common spotted ladybird (Harmonia conformis), a species found across the southern half of Australia, is a classic ladybird. The adult beetle is reddish-orange in colour with 20 large black spots, a distinctive dome- shaped body and it is about 10mm long.
Not all ladybird beetles are as brightly coloured as Harmonia conformis. Some species, such as the gumtree scale ladybird (Rhyzobius ventralis), are dark in colour and may go unnoticed in gardens. Other ladybird beetles, such as the minute two-spotted ladybird (Diomus notescens), may be overlooked because it is so tiny (about 2.5mm long).
Most ladybird beetle species and their larvae feed on prey, such as aphids, scale insects and mites. Ladybird beetles are strong fliers and can migrate considerable distances. They may arrive in your garden and stay to breed if there is adequate prey for them to feed on. If not, they will fly elsewhere. The single biggest disrupter to the activities of ladybirds and other beneficial insects is the use of pesticides, so minimising their use is the first step to encouraging these insects in your garden.
Every so often we see media reports about ladybird beetles in very large numbers. Last autumn, huge numbers of ladybird beetles were seen near Mount Gambier in South Australia. In this case, the consensus was that the beetles had arrived to feed on an infestation of Monterey pine aphids in timber plantations.
Some species of ladybird, including Harmonia conformis, may also form aggregations in winter or summer to avoid harsh weather. The beetles enter a period of dormancy and may be found clustered under tree bark or in dense shrubs. Have you seen these clusters in your garden?
Not all ladybirds are good bugs; some are leaf-eating pests! In Australia, there are about 10 species of leaf-eating ladybirds of the genus Epilachna. Common pest species, such as the 28-spotted potato ladybird (Epilachna vigintioctopunctata), are dome-shaped orange-coloured beetles with dark spots. They are very similar in appearance to several common species of beneficial ladybirds.
How do you tell which is which? Simple. If the beetle is chewing holes in the leaves of your vegetables, it’s a pest. Picking the beetles off is usually the best control method. If the beetle is hanging out among clusters of aphids, it’s a good bug and you have the first sign of a healthy functioning ecosystem in your own backyard.
It must be said that ladybirds don’t have it all their own way, with many predators and parasites that attack them. One parasitic wasp, Dinocampus coccinellae, has an intriguing life cycle. A female wasp lays an egg in a ladybird beetle and the hatching wasp grub feeds and develops inside the beetle. Before emerging from the host beetle, the wasp grub secretes chemicals that paralyse the ladybird. It then emerges and pupates between the legs of the still twitching ladybird beetle (see photo on page 1). After several days, an adult wasp emerges from the pupa. Incredibly, research has shown that about 25% of parasitised ladybirds recover normal behaviour after the emergence of the adult wasp!