How Do Ladybugs Tell the Weather?

Ladybugs, indicators of weather

A variety of cultural traditions reflect that ladybugs foretell the weather. There is some truth to these tales, as these insects are cold-blooded, meaning weather conditions affect their internal temperature, behavior and lifestyle. Ladybugs are active during a particular temperature range, and they are indicators of approaching seasons.

Background

Ladybugs are also called ladybirds or ladybird beetles. There are approximately 5,000 species in the ladybug (Coccinellidae) family around the world. Of the more than 400 species in North America, the most common is the seven-spotted ladybug (Coccinella septempunctata). Not all ladybugs are red bodied with black spots, like the seven-spotted version; some have stripes or no markings at all, and they can be red, orange, black, yellow and gray. Ladybirds are considered helpful to gardeners and farmers as they eat aphid pests.

According to Gary Booth, professor of integrative biology at Brigham Young University, "Ladybugs are cold-blooded, which means they're highly dependent on their environment." As a result, ladybugs hibernate during the winter, a state called diapause. Since ladybirds are greatly influenced by their natural surroundings, they are effective indicators of the weather.

Folklore

In the late 1800s, Elias Owen wrote about an old custom practiced in the neighborhood of Llanidloes, Wales, using ladybugs to predict the weather. When someone was lucky enough to hold one of the spotted creatures in the palm of his hand, he would chant a poem, then throw the insect up in the air. If it fell to the ground, then it would rain; but if it flew away, it foretold a sunny day.

In other European countries such as France and Austria, ladybirds are considered omens for favorable weather.

Physiology

There is an old proverb that reads, "When ladybugs swarm, expect a day that's warm." According to academic Markéta Vršková, there is truth to this dictum, although it involves the insects reacting to warm temperatures. If it is a hot day, the internal temperature of ladybirds then warms up, and this heat is stored in their shells. To thermoregulate, they fly to disperse the heat inside their bodies.

Temperature Range

Ladybugs are indicators of the day's temperature. According to Booth, "they have a narrow range of temperatures in which they can function." Generally, ladybugs will not fly if the temperature is below 55 degrees Fahrenheit.

Experiments conducted by Booth and his team at Brigham Young University while monitoring a native species ( Hippodamia convergens) and introducing Asian ladybugs (Harmonia axyridis Pallas) revealed that both species were more active at higher temperatures. However, interestingly enough, the exotic species was able to fly, reproduce and eat at lower temperatures than the native type. Booth raises the question whether the introduced species will eventually outcompete native ladybugs.

Winter

In North America, a sure sign that winter is coming is the apparition of swarms of ladybugs entering buildings and homes. Their search for a hibernation haven can occur anytime between September and November, where they search for cracks and crevices to use as entryways to a warm place for diapause. They usually will fly on a warm day toward their overwintering site, when the temperature rises high enough for activity after a period of cool autumn weather. If you have ladybugs sleeping in your home, you may see them roused and lively during the winter on an atypical milder day.

Spring

Swarm of ladybugs

In turn, ladybirds reveal the coming of spring, especially if they have been hibernating in your home. Once the weather starts to warm, they become awakened from their dormant state and start flying around to locate an exit point.

If the spring has seen frequent rain showers, an interesting phenomenon occurs. In Europe and North America, there have been accounts of sheaths of red substrates covered with hundreds of ladybugs. The Daily Camera reported the accounts of a local hiker in Boulder, Colo., whose daughter spotted a pine sheathed in ladybugs that turned the tough, brown bark into a "crawling red carpet." Since the spring had experienced extreme wet weather, there was more plant life available for aphids to munch on. With more aphids, ladybugs arrive in droves.

References

• Welsh Folk-lore; Elias Owen; 1887
• The Comparison of English and Czech Proverbs (Masaryk University Brno, Diploma Thesis); Markéta Vršková; 2007
• UK Entomology: Asian Lady Beetle Infestation of Structures
• Daily Camera: Boulder Mobbed with Ladybugs, Other Insects
• Brigham Young University: BYU Study Discovers Insights Into Ladybugs' Success as Fearsome Predators

Resources

• National Geographic Kids: Ladybugs