By Linda Ray
It is a sparkling, frigid day here in western Maine, but the sun is shining and it’s warm on a south-facing window upstairs. I hear my cats thumping around up there and go to investigate. As happens every fall, ladybird beetles (also called ladybugs or lady beetles) have sought a winter home in the minute cracks around this particular window. The light and southern exposure have lured them out of their sheltered nesting and onto the windowsill. Besides being a plaything for the cats, they are harmless though sometimes annoying inside our homes. However, giving them the credit they deserve, ladybird beetles are one of the most beneficial of garden insects, eating aphids, scales, psyllids, whiteflies and other soft-bodied garden and agricultural pests. They have come to symbolize prosperity, renewal and good luck.
Unlike moths and butterflies who as caterpillars form a cocoon or chrysalis respectively as the weather cools, ladybird beetles hibernate as adults. As their food supply diminishes, the days get cooler, and daylight decreases, they look for an overwintering site such as a rock crevice, a space under tree bark, in leaf litter or any sheltering abode. Normally solitary insects, they change their tune with the onset of cold. Once a winter site is found, a communication in the form of pheromones goes out to invite others of the same species to form a nesting colony or aggregation. It’s the more the merrier for winter survival as clustering together provides regulation of internal body temperature, protection from predators, and potential future mates. Because they have feasted on aphids and other soft-bodied insects since their larval stage, they have built up fat stores to survive the winter. It is at this point that they enter diapause or dormancy which lowers their metabolic needs but also makes them vulnerable. Being in an aggregation, also called a “loveliness of ladybugs,” gives them the best odds for survival.
In the family Coccinellidae, there are 12 different species of ladybird beetles identified in Maine, several native and the rest non-native. The few on my windowsill are non-native (Harmonia axyrides) or Multicolored Asian Lady Beetles (MALB) which are now considered invasive after having been imported in the twentieth century to help manage garden pests. While there is speculation that MALBs are contributing to the decline of native ladybird beetles, field research continues. The good news is that, if they come out of dormancy in your house, you don’t have to worry as they won’t damage homes or infest pets, lay eggs, or eat. However, the bad news is that this species may emit a foul liquid toxin (pyrazine) from their leg joints if threatened, that smells and tastes bad. Not so lovely.
Rest assured that, when the temperature reaches about 55 degrees in the spring, all species of ladybird beetles will be ready to reproduce and enter our gardens again. But that’s a spring story.
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Photo Credit:
Matthew.kowal, This file is licensed under the Creative Commons Attribution-Share Alike 4.0 International license.
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