Tuesday, March 9, 2021

What’s This Bug? The Asian Lady Beetle.

Close-up of an Asian Lady Beetle walking.
This little guy is the Asian Lady Beetle (Harmonia axyridis). They are a non-native species of beetle that was introduced to our country a hundred years ago in a well-intentioned, but not well-thought-out, effort to help soybean farmers control soybean aphids. They are voracious aphid-eaters, so they did that part of the job well. But, they have also aggressively pushed out native species of ladybugs. This is not only true in the US; they are taking over large parts of Europe and in the UK as well.

First, let’s get down to the naming thing (which, for some reason, many people get hung up on): Asian Lady Beetles and what we call ladybugs are both members of the insect family Coccinellidae. All members of this family are beetles, what we call them is simply a reflection of where we come from. In the US they are ladybugs; in the UK they are ladybirds and various places know them as lady beetles. Asian Lady Beetles can be referred to as a Harlequin Ladybugs/Ladybirds as well. So, any and all of these are species of one family, no matter what name you give them.

A side-by-side comparison of the Asian Lady Beetle on the left and the Ladybug on the right.
While what we know as ladybugs are very recognizable in their bright red and black spotted shells, Asian Lady Beetles wear a huge variety of different colors and markings. The white marking found at the base of the head (it looks like an “M” or a “W”) can be a good way to identify these insects, but not all of them have it. Asian Lady Beetles, which can have spots, no spots, or even stripes, have an orange and black color palette as opposed to the red and black of ladybugs. 
A display of the many variations of Asian Lady Beetles.

Many people point to two things that set Asian Lady Beetles apart from ladybugs - that they bite/are aggressive and that they smell. Both of these assertions are a bit hyperbolic.

Yes, Asian Lady Beetles have pincers and can bite when disturbed, but they do not attack. And their pincers are tiny, so their bite can’t really harm a person. However, some people do have an allergic reaction to the bite that can cause everything from cough to hives. People who are sensitive to these creatures may not even need to be bitten, touching a beetle then touching one’s eye has been known to cause pink eye.

 Asian Lady Beetles are often said to have a noxious odor. While they do secrete a goo that has an unpleasant odor when disturbed, this behavior is common throughout the ladybug world. It’s a defense mechanism known as reflex bleeding and is meant to discourage predators. The excretions of Asian Lady Beetles may be particularly gross to many people, but they no worse (or no better) than other ladybugs. That said, their particular goo is known to stain surfaces like walls, furniture, or fabrics. This all becomes a problem only when they begin to gather in large numbers, particularly inside structures.

Asian Lady Beetles crammed into a crevice of a house.

As winter approaches in temperate climates, Asian Lady Beetles begin to aggregate in ever-growing clusters to keep warm and seek out winter quarters. This is usually when they come into conflict with people because they tend to like the snug shelters that humans have made (why they choose human habitats is still under debate, this article gives some explanation). Once the beetles have chosen a spot to overwinter, they send out a pheromone trail that attracts others to their spot. This is why hordes of insects “suddenly” appear. These scent trails can last years, meaning some homes experience invasions every year. 

What’s a poor, beleaguered home-dweller to do? While the sight of large numbers of beetles in or around your home is disconcerting, they will not actually do any harm (unless disturbed, as previously mentioned). They do not bother food or belongings inside a house and they are not breeding either. They are simply hibernating for the cold months, after which they’ll move on to breed and feed. You should vacuum up the ones you can, but your best bet is to take action to keep them out, to begin with. During the still-warm days of fall, clear vegetation away from your house and seal it up well to keep Asian Lady Beetles and more out. Check out my blog on winterizing your home here.

Close-up of a ladybird beetle eating an aphid. Photo by Alexandre Debieve on Unsplash.
It’s important to not view Asian Lady Beetles as “bad”. Yes, they are invasive, but they are here to stay and they are extremely effective at controlling pest insects on crops. Supplies of the type of ladybugs we sell (Hippodamia convergens) are dwindling rapidly. Some of this is due to invasive species, but the ones we get nest in the mountains of the West Coast and the devastating fires of the last few years have nearly wiped them out. It’s time to embrace other types of ladybugs that have the exact same eating habits. This includes not only the Asian Lady Beetles but lesser-known native species. Here is a fun project that helps educate people on the different species and locate “lost” species.

Asian Lady Beetles swarming.

Take Care

Submitted by Pam




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