Ladybugs, with their distinctive spotted shells, are often seen as symbols of good fortune and beneficial insects in gardens. Many people wonder if these familiar beetles are facing threats to their survival. While the term “ladybug” is widely recognized, the answer to their endangerment is more complex than a simple yes or no, as it depends on the specific species in question.
Ladybug Diversity and Population Trends
The common name “ladybug” refers to a diverse group of beetles within the family Coccinellidae, with around 5,000 species globally. In North America, ladybug populations have shifted notably. While some non-native species are thriving, many native species are experiencing significant declines. This distinction is important: overall numbers may not decrease, but species diversity is declining.
For example, native species like the Nine-spotted ladybug (Coccinella novemnotata), the Two-spotted ladybug (Adalia bipunctata), and the Transverse ladybug (Coccinella transversoguttata) have all experienced sharp declines across their historic ranges. In contrast, non-native species such as the Multicolored Asian ladybug (Harmonia axyridis) and the Seven-spotted ladybug (Coccinella septempunctata) have become dominant. These introduced species, often brought in for pest control, have rapidly expanded their populations, sometimes displacing native counterparts.
Pressures on Ladybug Populations
The decline of native ladybug species is influenced by several factors. A primary pressure is the loss and fragmentation of their habitats. Urban development, agricultural intensification, and the conversion of natural areas can reduce the availability of living spaces for ladybugs. This habitat destruction can also limit their access to food sources and overwintering sites.
Pesticide use, especially broad-spectrum types, poses a significant threat to ladybug populations. These chemicals directly kill ladybugs, which are natural predators of many garden and agricultural pests like aphids. Even if not directly lethal, pesticides harm ladybugs by reducing prey or affecting reproduction.
Competition from non-native ladybug species is another factor contributing to the decline of native populations. The Multicolored Asian ladybug is known for aggressive predatory and competitive abilities. It outcompetes native species for food and engages in intraguild predation, eating the eggs and larvae of other ladybug species. This invasive species also carries a parasitic microsporidian; it is immune, but the parasite can be lethal to native ladybugs if consumed.
Climate change also exacerbates these challenges. Rising temperatures and heat waves directly impacts ladybugs by causing dehydration, disrupting metabolic processes, and reducing appetite and reproduction. Temperature changes also affect prey availability, as aphid populations may decrease or shift. Climate change can also lead to habitat fragmentation, making it harder for ladybug populations to adapt or find new areas.
Supporting Ladybug Populations
Individuals can take practical steps to help support native ladybug populations locally. Reducing or eliminating the use of broad-spectrum pesticides and herbicides in gardens and yards is an important action. Opting for organic pest control methods protects ladybugs and other beneficial insects. Allowing some aphid populations to persist also provides an early food source for ladybugs, encouraging them to stay.
Creating ladybug-friendly habitats is another effective way to provide them with resources. This involves planting native flowers and plants that offer food (pollen and nectar) and shelter. Flat-topped flowers like yarrow, dill, fennel, and marigolds are particularly attractive to ladybugs. Providing overwintering sites, such as leaf litter or simple wood shelters, gives ladybugs a safe place to hibernate. A shallow water source, like a dish with pebbles, also helps keep them hydrated.