A little girl came by the greenhouses with her parents this past weekend, excited about seeing some ladybugs. She thought they were pretty, but she didn’t know whether she wanted them on her plants. I told her they were one of my favorites because they eat bad bugs and that I’d write about them this week.
Lady beetles (Coccinella sp.) are one of the most recognizable and prevalent beneficial insects. There are over 450 species in North America. Only the Mexican bean beetle and the squash beetle feed on plants. All other lady beetle species eat soft bodied insects like aphids, mealybugs and thrips. These attack our crops, garden flowers and houseplants. Lady beetles also eat moth eggs, pollen and nectar.
Adult females lay their yellowish eggs on the undersides of leaves in clusters. Individual beetles can lay as many as 1000 eggs. Some deposit them for up to three months.
These hatch into larvae that look a little like tiny alligators. Most are some shade of bluish gray with orange markings. Some people think these crawling baby ladybugs are plant pests and kill them, so it’s important to learn to recognize them. Your computer can help.
In three to four weeks these immature insects grow to almost half an inch long. They usually molt or shed their skin four times. During this time these voracious critters can consume as many as 300 crop damaging aphids.
At the end of the larval stage these insects enter the pupa or resting phase of their lives. They usually attach themselves to the underside of a leaf or twig and remain there for a few days to nearly two weeks. Adults emerge, mate, and the reproductive process starts all over again. Adult beetles usually live for a few months, but some can stay active for over a year, consuming crop damaging pests the whole time.
The most common species I see around here is the seven spotted lady beetle (Coccinella septempunctata). It is also one of the more efficient pest controllers. Populations are active from mid-spring until fall.
Sometimes gardeners purchase lady beetles to control pests in their gardens, since companies brag about the voracious nature of these bright red eating machines. This seldom works out as well as advertised. The beetles often fly to greener pastures so to speak, if a heavy pest population isn’t present. Also, beetles reared in dense populations are more likely to be parasitized by other insects.
Ladybugs can be overly friendly, especially in the fall. They are just trying to avoid the cold weather. They don’t cause damage to our homes, but they still can be a nuisance, since they often accumulate in large numbers. If they enter your home don’t kill them with fly swatters or similar means. You’ll be sorry.
Ladybugs emit a strong odor when smashed. That’s probably one reason other insects don’t prey on them. I suggest vacuuming them up and disposing of them outside. Most will probably die but that’s nature. During the summer they’ll certainly earn their keep.
Ted Manzer teaches agriculture at Northeastern High School.