Saturday, November 11, 2017

Asian Ladybugs



This story starts with an inquiry from Lori Herring and her 2nd and 3rd grade students at Marshfield R1 School.  They were studying trees and found the maple leaf above with something on it they couldn't identify by field guides.  A first guess was an Asian ladybug larva but there was more to the story.


Early larva

Zooming in you can see a little beyond halfway down that the larva is splitting its skin down the back to expose the pupa.  Notice the spiky features at the front, the remains of the last larval stage to the right.  This is the last step in its metamorphosis before it emerges in the fall to start to torment us.  Arkinspace.com describes this step in the life cycle: 

"When the larva has grown to its full size it will then attach itself to the stem of a plant. It splits along its backside and exposes the pupa underneath. This sounds like something out of one of the “Alien” films and it really doesn’t take long to figure out that they didn’t get those ideas straight out of their imagination! The pupa, though, is wrapped up in this final stage of its metamorphosis and so is safe from the elements – but not from predators. It is at this stage it is at its most vulnerable. If approached close to its hatching time by a possible predator it will shake itself dementedly to try and warn off the unwelcome visitor! This last stage takes just a few days and then the adult ladybug is ready to emerge."
Larval stage
Now back to the "torment."  This is the Asian ladybug, Harmonia axyridis, actually a beetle as all "ladybugs" are.  It is most commonly known as the harlequin, multicolored Asian, or simply Asian ladybeetle in the Coccinellid family.  Unlike our "ladybugs" beloved in children's stories and merchandise, these are no "ladies."

Last week, shortly after the first hard freeze of the year we had the sudden return again of swarms of these ladybeetles on the sunny side of the house, the trees and my neck.  There are those annoying little nips on the neck and arms and when I swat or brush them away I am left with a stink on my hands.  Why now?  Tim Smith answered the question in the Missouri Conservationist Ask the Ombudsman column several years ago.
"Each fall, during a warm-up following the first cold weather, the insects gather on the sunny sides of houses and other structures as they look for cracks and crevices where they can find shelter from the coming winter.  Many will survive the winter and appear again in the spring as temperatures warm and they try to exit the house."
According to Wikipedia, they were brought to the United States in 1916 to control insect pests of plants, but were not successful.  In 1988 they were observed in numbers in New Orleans, and since then they have spread.  By 1995 they were occasionally found in the Midwest and became common in 2000.

They cluster by the hundreds in protected spaces
Subsequently, they have also contributed to the decline in native ladybugs, presumably by out competing them.  They also have reached pest status to the higher biped mammals, i.e. us, both because of the swarming numbers, their little bites and unpleasant odors and the tendency to move into our buildings.  For information on these pests including control recommendations, check out this Ohio State site.
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Arkinspace.com has detailed photographs of their various life stages from egg to annoying adult.

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