Everyone knows what a ladybug is. That bright, domed beetle-like creature covered in spots and dots is prized by gardeners, cherished by children, despised by some homeowners, and even emulated in the design for the infamous VW Bug. But what exactly are ladybugs and how does one entice them into the garden or drive them from the woodwork when they become invasive pests in the fall?
First of all ladybugs, sometimes known as ladybirds, are not true bugs at all but rather beetles belonging to the Coccinellidae family in the suborder of insects known as Polyphaga. Other members of this group include weevils, checkered beetles, leaf beetles, and longhorn beetles. Although there are millions of beetle species worldwide, none holds such an honored place in the hearts of humans as the simply elegant and useful ladybug.
Worldwide there are more than 5,000 species of ladybugs, with 450 of them being endemic to North America. And while the ladybugs of our childhood are always the classic red with black spots, they actually come in many colors including pink, red, orange, yellow, black, brown, rust and grey. An old wives’ tale says that you can tell the age of a ladybug by the number of spots on their wings, but the truth is that the number of spots present depends entirely on the species, with some having as many as 24 and others having none at all. And while the spots do fade as the beetle ages, ladybugs only live for about a year.
The bright colors of ladybugs are admired by humans, but to their predators these colors scream, “I might be poisonous!” And should a ladybug be disturbed or frightened, they may exude a bit of orange-colored blood from the joints in their exoskeletons. This blood contains a fragrant, toxic alkaloid fatal to some types of insect and bird predators (but not humans). I actually find the smell of this alkaloid quite pleasant because it reminds me of cilantro – one of my favorite spring herbs. Should a predator not be repelled by the ladybug’s warning color, smell and taste, they will often be confused by the beetle’s ability to “play dead”. And if that doesn’t work, ladybugs will simply roll off of their perch in a swift and confusing fall.
Although ladybugs are good at evading predation, they and their larva are voracious predators themselves, consuming multitudes of aphids, scale insects, plant mites, mealybugs and whiteflies. But in the early spring when insects are most scarce, ladybugs rely on flower pollen as a source of food.
While the adult form of ladybugs is widely recognized, the larval form is not. Best described as alligator-like, the black and orange-spotted larva are shaped like elongated triangles and sport spikey protrusions along their backs. When the larvae first hatch from clusters of tiny orange, cylindrical eggs laid on the undersides of leaves they are incredibly small and slender. Over the next several weeks they shed their exoskeletons up to seven times – each time becoming larger and longer. Larvae eat just as many insects as the adults, but if not present, the larva will eat the eggs and larva of their own species. And because of their odd – some might say creepy – appearance, ladybug larvae are often mistaken for pests and killed.
Once the larva have completed the molting phases known as instars, they undergo a complete metamorphosis – exactly like a butterfly. The larva attach themselves firmly to a leaf or other object and again the exoskeleton hardens. In 7-14 days the fully formed ladybug emerges pale and spotless from its pupa. It takes about 10-24 hours for the wings and wing covers dry and harden during which time the colors deepen and the spots appear.
Like all wild creatures, ladybugs have an impeccable sense of timing and soon after metamorphosis is complete, they fly out in search if their favorite food. I always look for ladybugs when my corn begins to silk – and surprisingly they always show up just in time to eat the aphids that feed on the succulent threads. But not every gardener is so lucky and many gardens go year after year with no ladybugs at all. Some go so far as to purchase ladybugs from mail-order catalogs, but if the right conditions don’t exist for their survival in the garden, the ladybugs will simply fly away to one that does.
There are several things gardeners can do to make their gardens more enticing to this beneficial insect. The first and most important is to avoid using pesticides, even natural ones, which kill both adult beetles and larva. Secondly, plant flowers that produce the types of pollen ladybugs use as an early spring food source. These include members of the Apiaceae (carrot) family, such as cilantro, dill, fennel and Queen Anne’s lace; those of the Leguminaceae (legume) family, such as peas, vetch, buckwheat and clovers, and species of Asteraceae (aster) including coreopsis, cosmos, daisy, and coneflower.
Once a population of ladybugs moves in for the summer feast, encourage them to stay around for winter by providing warm, dry, sheltered places in which to hibernate. In the wild ladybugs hide primarily under the bark of trees and dry leaf litter. If the area around the yard doesn’t provide the right kind of hibernation environment, some have found specially designed ladybug houses do the trick.
Before you decide to encourage large numbers of overwintering ladybugs in your yard, be aware that there is a difference between native ladybugs and the non-native Asian species known variously as the Asian-, Japanese-, Harlequin-and Halloween ladybugs (Harmonia axyridis). These invasive ladybugs spread rapidly after being introduced as a natural pest control measure in pecan orchards in the deep south. The often-sited assumption that the local climate would not be conducive to their reproduction seems naive at best, as the deep south and Asia share similar climates. Regardless, these aggressive non-native species are here to stay and reproducing at an alarming rate and entomologists are concerned that the invasive Asian ladybug is displacing the natives.
Moreover, homeowners too, are increasingly reporting this species as pests in their own right. Much more aggressive than the native species, the Asian ladybugs and their larva tend to bite, which doesn’t really hurt, but can be surprising. And while native species such as the Convergent ladybeetle (Hippodamia convergent) can invade homes, the aggressive Asian species is almost twice as likely to do so.
I have lived in a house that seemed to have been a perennial favorite for all of the ladybugs in a ten-mile radius. The white siding on the south-facing wall was the perfect hibernation site and in the fall ladybugs would stream in by the thousands. Eventually some of the ladybugs found their way inside and they would spend the days crawling around sunny windows or huddling in the corners of the ceiling. And while at times the they were a distraction, they did no real damage. We controlled their numbers easily enough with a stick vacuum, releasing them on warm sunny days.
So while they can sometimes give us headaches, both native and non-native ladybugs are beautiful beneficials that provide organic gardeners with an unsurpassed level of free, natural and effective pest control while providing young people with the lifelong understanding that bugs can be good and friendly and beautiful all at the same time.