Ladybug, Ladybug Fly Away Home

At another stop, midway down Invergordon Street, we learned about “keystone” trees and how important they are in our diverse, healthy forest ecosystem. We also learned not to panic when we see caterpillars and insects eating leaves and branches, because they are part of the food web, and will be consumed by insects, birds, bats and mammals as a vital part of their diet. It’s the circle of life!

There are many types of ladybugs that can be found along the Riverwalk, but unfortunately the one that dominates is the Asian lady beetle, a real disrupter and intruder. It looks similar to the native lady beetles, but you can tell the difference because it has 15 black spots on a reddish orange body and has large white spots on its cheek area and a white ‘W’ or an ‘M’ shape on the top of its head.

It’s a generalist not a specialist, which means it’s not fussy about what it eats or where it lives or how cold it gets during a Canadian winter. It can live in the forest, the wetland or even cluster, in large numbers, in your shed or house. They eat aphids, mealy bugs and mites that harm the fruits, flowers and vegetables prized by gardeners. This is why it was introduced to Canada as a biological pest control in the 1970s . It was soon discovered, however, that this import was surpassing the native ladybugs in numbers and disrupting nature’s balance. The Asian lady beetle breeds faster and is a better hunter than the native lady beetle and has driven the native species to the margins.

Asian lady beetles have also been found to be a pest in commercial fruit orchards infesting trees and gorging on fruit. Despite good intentions, introducing the highly aggressive Asian lady beetle to North America has thrown chaos into a once stable state of co-existence between species and is causing more problems than its introduction set out to solve.

Native Pink and Twelve-spotted lady beetles can also be found in our gardens preying on plant eating insects. To learn more about native lady beetles here is some information from the Haliburton County Land Trust: https://www.haliburtonmastergardener.ca/wp-content/uploads/2022/07/Lost-Ladybugs.pdf

U-Links Species Profile:

Asian lady beetle, Harmonia axyridis

Ladybugs are valued by gardeners because they eat the aphids, mealy bugs and mites that harm the fruits, flowers and vegetables prized by gardeners. Ladybugs are bred and sold as biological control agents replacing harmful insecticides to control populations of undesirable insects. There are many types of ladybugs that can be found in urban wildlife areas such as the Minden Riverwalk. Of these however, an elusive intruder has cemented its place in the local ecosystem and while it can be beneficial it also has a dark side. It is the non native Asian lady beetle (Harmonia axyridis).

Brought into North America originally as a pest control agent (Brown et al, 2008), this invasive species was originally native to China, Japan, Korea, eastern Russia, Mongolia and Siberia.The Asian lady beetle has characteristics similar to that of the native ladybugs we have in Canada so you would be forgiven if you misidentified it. There are many variations in colour and spot pattern, although they commonly have 15 spots. The Asian lady beetle typically has a reddish-orange carapace which looks similar to that of their native counterpart, however the Asian lady beetle has large white spots on its cheek area and a white ‘W’ or an ‘M’ shape on the top of its head (Environmental Pest Control, 2023), and are roughly 7mm in length.

The Asian lady beetle can make its home in a wide range of habitats such as forested areas, wetlands, savannas as well as clustering in huge numbers in sheds and houses. This makes it a generalist because it can live almost anywhere and eat a range of insects. (Brown et al., 2008).

This invasive species creates a problem for the more laid back native species because it is multivoltine, meaning it can have more than one clutch of offspring per season which the native beetle cannot (Brown et al., 2008). This allows for their numbers to surpass those of the native species very quickly. They will also outcompete the native species for resources essential for survival. Their insatiable appetite makes this species an incredibly effective hunter, a better hunter than the native species which allows it to dominate available resources and create an unwelcome disturbance in the food web. (Koch & Galvan, 2008). Furthermore, although they eat the so-called nuisance insects they don’t discriminate and can greatly reduce the numbers of beneficial insects as well, something the “live and let live” native species doesn’t do. Asian lady beetles have also been found to be a pest in commercial fruit orchards infesting trees and gorging on fruit. Despite good intentions, introducing the highly aggressive Asian lady beetle to North America has thrown chaos into a once stable state of co-existence between species and is causing more problems than its introduction set out to solve.

Researcher: Caleb Brown, Trent University