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Monday, February 22, 2016

Ladybugs, Lady Beetles or Ladybird Beetles. How Good are They?

Polished lady beetle. © Beatriz Moisset. 2012
 What is in a name? Most call it a ladybug; others, ladybird or ladybird beetle or just lady beetle. Is one name more appropriate than others? Is there just one kind, or many kinds of this insect? Scientists prefer the term Coccinellidae to include all the members of this large family of beetles. The technical name has the advantage of leaving no room for confusion.
Seven-spotted Lady Beetle (Coccinella septempunctata). © Beatriz Moisset. 2013
 Ladybug is not entirely correct because “bugs” are insects with sucking mouth parts and simple development. “Ladybugs” are, in fact, beetles, with chewing mouth parts and with a full metamorphosis, with larva, pupa and adult, similar to that of butterflies. So the preferred common name is lady beetle.
Now that we settled this, we can move on. If you are thinking of just one generic lady beetle, think again. The 500 species of lady beetles in North America vary in size from a pinhead to almost half an inch. They are not all red with black dots; some are entirely black or mostly red or have a pattern of black and ochre or black and yellow.
Most feed on aphids and other small, juicy insects, and we love them for that. But a few of them feed on plants, to gardeners’ disappointment. A handful of species feed on mildew. The babies, or larvae, are as ugly as the adult is pretty (well, I find them beautiful anyway). They look like little alligators. If all this shocks you a little, you may want to spend a couple of minutes digesting it.

Spotted lady beetle larva (Coleomegilla maculata). © Beatriz Moisset. 2013
 Most of those 500 species of lady beetles are native to North America; but a few dozens came from other continents. Some arrived accidentally, but others were brought to combat pests. The first one of these intentionally-introduced pest enemies was the Vedalia beetle, Rodolia cardinalis, brought from Australia in the 1880s to fight a non-native pest, the cottony cushion scale. This scale insect was devastating the orange groves of California.
The introduced lady beetle was such a resounding success that it inspired horticulturists to start using other insects as pest controls, also called biocontrols. Some of the newcomers are doing a satisfactory job, especially the ones that help control non-native green-house pests. It is too bad that sometimes we learn the hard way about unintended consequences. Not all introduced species continue to be well behaved guests. Some develop into unwanted pests themselves.
You will not like what I am about to tell you because I am sure you have seen this lady beetle and delighted in it, thinking that it is a good friend of your garden. The Asian lady beetle, Harmonia axyridis, has been in North America for almost a century. It was brought from Asia because of its voracious appetite for aphids. We can’t deny that it goes through them with gusto.
Asian lady beetle invasion in winter. © Beatriz Moisset. 2009
 Unfortunately, its population has grown explosively since its arrival and, once established, it revealed some undesirable habits. It is larger than most native lady beetles, so it has no trouble including them into its diet, and it may be endangering some of them. The Asian lady beetle has become a nuisance in another way. When winter comes, it looks for a place to sleep, often gathering in large crowds in garages and attics. No wonder Europeans are trying hard to stop this invasion. It is too late for us, though.
The concept of using lady beetles has spread to ordinary gardeners, who see advertisements and decide to purchase some. This is not as desirable as it seems at first sight. You can find some good advice at the  North Carolina State University website, University of Wisconsin website and About.com.. Purchasing lady beetles may be unnecessary if you maintain a healthy garden (no pesticides) which invites the local lady beetle fauna. Moreover, a healthy garden welcomes other allies in the war against aphids, such as lacewings, syrphid flies and parasitic wasps.
If you still insist on buying lady beetles, beware! Most sites that sell them provide insufficient or false information. Some don’t mention which species they are selling, as if all lady beetles were the same. They are not! They fail to inform you where they were collected, or whether they were bred. A few provide the wrong instructions for releasing them.
Convergent Lady Beetle (Hippodamia convergens). © Beatriz Moisset. 2013
 Stay away from the non-native Asian lady beetle. Find the origin of the insects you buy. Just as with native plants, you want to choose the locally native ones. Convergent lady beetles are usually harvested from their wintering sites in California.  The lady beetle market may represent a threat to their populations. Moreover, these lady beetles are not inclined to stay in your garden. Their instinct tells them to fly away from the crowd that was sharing their wintering places. Few or none will remain in your garden. Also, these transported lady beetles may carry pests and introduce them to new places.
Eggs of unidentified lady beetle amidst a colony of aphids, also a beautiful sight. © Beatriz Moisset. 2013
We may go on loving lady beetles and being grateful for their services. Let us love the native ones and make the effort to create the right habitat for them, including some sustenance, as Christy Peterson reminds us with a touch of humor.
 
© 2014, Beatriz Moisset. First published in Native Plants and Wildlife Gardens.