The Mildew-Eating Lady Beetle

As most of you probably know by now, I’m obsessed with photographing insect life cycles.  I’m not satisfied until I have all the pieces of the puzzle.  If I find eggs, I want to know what hatches out of those tiny little packages of life.  If I see a grub or a caterpillar, I want to know the end result of its metamorphosis.  I enjoy being a citizen scientist.  Every trek into my own backyard is an adventure of observation and discovery.

Mystery Eggs

1 20-spotted lady beetle -EGGS

I grow nectar-rich zinnias in my beautiful wildlife garden to attract butterflies, bees and hummingbirds.  Unfortunately, around this time of year they also host powdery mildew.  One day I found a group of tiny white eggs that had the same shape as ladybug eggs.  So I put the leaf into a plastic container to join my “critter protection program” and took them into my house to raise by hand.

Feeding the Larvae

20-spotted lady beetle -LARVA-

A few days later the spotted larvae emerged.  They looked very similar to ladybugs so I figured they must eat aphids.  I collected some live food and waited, with camera at the ready, for them to hunt down their prey.  But they showed no interest whatsoever in those juicy little aphids.  Now I had a mystery on my hands.  I didn’t want to be a bad “bug mommy”, so I hunted and gathered other tiny insects and added them to the nursery container.

3 20-spotted lady beetle -LARVA

The Disappearing Mildew

The next day I noticed the larvae had grown, but no “feeder” insects were missing from the container and there were no bite marks on the zinnia leaf.  So I set the leaf out on a table, steadied my camera and took a in-your-face shot of a larva.  Imagine my surprise to see it was actually eating the powdery mildew!  Over the next week I provided new mildew-covered leaves for my little guys and gals to munch on and waited to see what would happen next.

20-spotted lady beetle -PUPA 1

Time to Pupate

When the larvae reached maturity they “glued” their backside to the surface of a leaf and shed their skin, revealing the pupa underneath.  Except for the obvious color difference, they looked just like a tiny version of a ladybug.

20-spotted lady beetle -PUPA 2

The 20-spotted Lady Beetle is born

After a week or so the tiny beetle emerged from its pupa shell.  Now I had all the pieces of the puzzle and it was time to get online to find the proper name for my new discovery.  I learned it’s called the 20-Spotted Lady Beetle or the Mildew-Eating Beetle (Psyllobora vigintimaculata).  And by the way, both the larva and the adult chow down on the mildew.

20-spotted lady beetle --ADULT---

Now I’m a happy bug nerd !  I’ve learned something new about my own backyard and photographed all of the life cycle stages.  Time to see what else I can find out there !

20-spotted lady beetle -ADULT


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  1. says

    How wonderful- a bug that eats mildew! I never knew there was such a thing. Wish I had some of those in my garden, as my zucchinis and pumpkins used to always get yucky with powdery mildew around this time of year.

  2. Joyce Barnhart says

    Who knew there was such a critter?! Thank you so much, Judy. Now that you have that super lady bug, you might not want to get rid of its food, but if you do – I’ve benn successful using a spray of half skim milk, half water to control and prevent downy mildew on curcubits. Nice organic answer to the problem, though not as nice as your ladybug.


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