Even people who don’t like insects are usually fine with ladybugs. We usually encounter them first in childhood in storybooks or in the garden. They don’t bite or sting and they aren’t scary big. Even better, they don’t eat our vegetables and flowering plants, but instead attack those insects who do. What’s not to love?
Here on 20th Street we see what is most likely the multicolored Asian lady beetle. Some have spots and some don’t. They may range from yellow to orange to red in color. The color and number of spots are not an indicator of age – in fact, a “baby” or “adolescent” ladybug doesn’t look like an adult at all.
(Photo 2: ladybug larva)
Ladybugs go through 4 stages of development (called “instars”): egg, larva, pupa and adult. The eggs look like small yellow ovals. After 4 to 10 days, the larvae that hatch are red and black, but that is the only resemblance they have to their future adult selves. They have no wings and little spiky-looking growths all over their body. Although it may look creepy, if you see this bug in the garden, don’t kill it! It will grow up to be a ladybug. Other species of ladybug may be yellow and black or orange and black, and slightly smaller or larger. Once you start to notice the shape of the Asian ladybug larvae, you will likely recognize the larvae of other ladybug species too.
(Photo 3: ladybug pupa)
For the next 10 to 14 days, the larvae grow in size, shedding their skins (“molting”) about 5 to 7 times along the way. They grow this way because their skeleton is on the outside of their body so it has to break open and re-form each time the insect gets larger. At the end of the larval stage the ladybug attaches itself to something stable to go through the changes necessary to become an adult. This is called the pupal stage. Moths and butterflies do this too.
The ladybug remains in the pupa for 7 to 14 days and emerges as a soft-bodied adult. As the exoskeleton hardens, the colors brighten and the ladybug is now the adult we recognize.
(Photo 4: Ladybug, in lower center eating aphids)
Ladybugs do not build nests, instead they congregate where the food is – mainly, aphids. Aphids are insects that cluster on leaves and stems, sucking plant juices and causing stress to the plant. They also produce a sticky sap known as honeydew which can be a nuisance. Aphids are undesirable, but if we have no aphids we will have no ladybugs either. The trick is to have enough ladybugs around to eat the fast-reproducing aphids. On 20th Street the Wild Lilac (Ceanothus) shrubs have aphids, so that’s where we see the most ladybugs. They are rarely seen on other plants on this block.
You can buy ladybugs for your garden, but remember the adults have wings. If there are not enough aphids for them all to eat, they will fly away. If possible, it’s better to buy ladybug larva, which are just as hungry as the adults and won’t fly away for a while.
Ellyn Shea is a gardener and garden consultant in San Francisco.