Ladybugs are members of the Coccinellidae family. The Latin translation means ‘scarlet.’
In the US, they’re called Ladybugs. In Europe, they’re Ladybirds. Legend (or internet rumor) says in the middle ages in Europe, farmers prayed to Mother Mary to save blighted crops. Prayers must have been made in spring because Ladybugs came along to save the day. In this case, ‘Lady’ or ‘Lady’s birds’ refers to Mary Mother of Jesus. Their German name – Marienkafer, translates to Mary Beetles.
In North America, there are 450 species of Ladybugs with California hosting at least 175.
The Convergent Ladybug is native to the North and South American continents. It is easy to identify by convergent (or intersecting) white lines on the pronotum, behind the head.
Solitary for most of the year, Ladybugs like to be near water and ponds. They congregate around food sources which can occupy forests, grasslands, suburban gardens, and agricultural fields.
All Ladybug species prey on soft-bodied plant suckers such as;
- scale insects
- plant mites
They’ll also eat;
- stinkbug eggs and larvae
- asparagus beetle eggs and larvae
- potato psyllid eggs and larvae
- their own eggs and larvae
In the fall, when Ladybugs are preparing to go into diapause, adults will eat pollen to gain extra fat.
Adult ladybugs can eat nearly 50 aphids per day and 5,000 over a lifetime.
Convergent Ladybugs have a special ability to modify their development in times of food scarcity.
Ladybugs use a sense of smell (with antennae) to detect pheromones secreted by aphids and other prey. They also have good eyesight.
They’ve been clocked at flying up to 37 miles per hour!
Bleeding Joints, a Defense Mechanism
Like other animals with flashy coloration, this communicates poison. The Ladybug is no exception. When frightened they produce an (alkaloid) chemical that causes a yellow stain. It’s secreted from their joints and has a bitter taste and foul smell. (Larval forms secrete it from the abdominal area.)
Another type of defense is playing dead. Pulling vulnerable legs under its hard shell, a Ladybug can withstand small scale attacks.
Life Cycle and Life Span
Females generally lay between twenty to thirty eggs at one time.
They have two reproductive cycles a year, in spring and fall.
Females will lay eggs in aphid beds so larva have a ready food supply.
All life stages can be found together at the same time.
Adults live for one year. However, temperature and food sources may alter this. In cooler temperatures, adults have been observed living for up to three years.
Ladybug predators include birds and other beetles. If a Ladybug gets too close to an ant colony, they will attack. One-on-one ant and Ladybug relationships are dismissive but polite.
Insect Hibernation – Diapause
When temperatures drop, Ladybugs fly up! High above the ground, wind blows them into the hills (see Ladybug Wash-Ups in Resources below).
Aggregate site selection may be a combination of long-chain hydrocarbons left by previous winter gatherings as well as pheromone sensing. They also seem to enjoy places that receive warm sun rays.
Once temperatures drop below 55º, ladybugs stop flying. Aggregation is for warmth and mating.
Estimates of 37 million beetles have been observed in some aggregate locations.
Biological Pest Management – Invited Invasive Species
In the late 1800s farmers began experimenting with natural predators to control insect infestations. In the 1920s Southern California citrus growers imported Australian Ladybugs to combat mealybugs.
Between the 1920s and 1980s American farmers released imported Asian ladybugs in pecan, pine and soybean crops. (The native home-range for the Asian Harlequin is eastern Asia – Siberia and Russia through the Himalayas, China, and Japan. ) Now, Asian Ladybugs – Harmonia axydris, though beneficial, are considered one of the worlds most invasive beetles.
The Harlequin beetles are stronger than the native species. They compete for the same food sources. A success factor may be a single-celled parasite that lives inside them. It exists in all life stages from egg and larva to adult. It’s harmless to the Harlequin but deadly for other species especially if they eat their eggs and larvae.
Asian Harlequin beetles have a problematic habit of aggregating on or in homes. They prefer light-colored buildings and seem to like window screens.
When frightened or disturbed, Asian Harlequin’s may bite, as well as release their chemical defense.
If trapped in food, grapes, or wine they contaminate it with bitter ‘ladybug taint.’
To remove Asian Ladybugs, it’s best to wait until it’s cold and use a vacuum cleaner to suck them into a nylon stocking.
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American Journal of Enology and Viticulture – Influence of Harmonia ayridis on the Sensory Properties of White and Red Wine
Animal Diversity – Hippodamia convergens
Ask an Entomologist – Ladybug Declines in the US (comparing museum collection data)
Bay Nature Magazine – When Thousands of Ladybugs Gather in the Park
Cornell University – Multicolored Asian Lady Beetle – Insect Diagnostic & Pest Management (PDF)
Hearts Pest Management – Asian Lady Beetles vs. Native Ladybugs
Journal of Insect Science – The multicolored Asian lady beetle, Harmonia axyridis by R.L. Koch –
Ladybug Planet – Do Ladybugs Eat Ants? When Ants and Ladybugs Clash!
National Geographic – Learn how the ladybug’s big appetite is a boon to many farmers. Find out the real purpose of their familiar polka-dot pattern.
Nature – Invasive ladybird has a biological weapon by Ed Young
Oxford Academic – Environmental Entomology – Olfactory Response of the Lady beetle Hippodamia convergens
Writing for Nature – The Beneficial Lady Beetles: Good Luck Bugs or God’s Little Cows
Penn State College of Agricultural Sciences – Department of Entomology – Multicolored Asian Lady Beetle
Research Gate – University of Florida – ConvergentLady Beetle Hippodamia convergens (PDF)
Science Direct – Elytron
Science Direct – Beneficial Insects (Ladybug introduction to California) – History of Insect Pathology
ThoughtCo – 10 Facts about ladybugs
University of California at Berkeley – History of Biological Control (PDF)
University of Minnesota – Multiclored Asian Lady Beetle
Wikipedia – biological pest control
Wikipedia – Coccinellidae
Wikipedia – Harmonia axyridis
University of California Division of Agriculture and Natural Resources – Natural Enemies Handbook
*Biologists speculate that wash-ups are caused by winds blowing in the wrong directions when Ladybugs are preparing to diapause. (Insect hibernate)