“Brown ladybugs” typically refers to specific insect species with brownish hues, not a single type. While familiar red ladybugs are recognized, many species within the Coccinellidae family (lady beetles or ladybirds) display colors like orange, yellow, and brown. These brownish insects share characteristics with their red counterparts but have unique features and behaviors. Understanding these differences aids identification and management.
Common Brown Ladybug Species
The multicolored Asian lady beetle (Harmonia axyridis) is the most common insect referred to as a “brown ladybug.” Native to eastern Asia, it was introduced to North America and Europe for pest control. Adult Asian lady beetles measure between 5.5 and 8.5 millimeters, often larger than native species. Their body is a moderately convex, shortened oval.
Coloration and spot patterns of Harmonia axyridis vary widely, from pale yellow-orange to red, including orange-brown or tan. They can have zero to 22 black spots of varying sizes on their wing covers (elytra). Some forms are even uniformly black with red spots. The variations in color and spot count can make identification challenging.
Other brown ladybug species exist but are less commonly mistaken for home invaders. Examples include the larch ladybug (Aphidecta obliterata), light brown with an “M” mark on its pronotum (3.5-5 mm). The cream-spot ladybug (Calvia quattuordecimguttata) has a walnut-brown body with 14 white spots. The painted ladybug (Mulsantina picta) exhibits mottled brown and gray patterns and is found in pine forests. These species remain outdoors and do not typically invade homes.
Distinguishing Features and Behavior
Distinguishing Asian lady beetles from native ladybugs involves observing physical and behavioral traits. A prominent feature of the Asian lady beetle, especially the orange-brown form, is an “M” or “W” shaped black marking on its pronotum (the white area behind its head). Native ladybugs often have a black head and thorax with small white dots on the sides, lacking this distinct M-shaped mark. Asian lady beetles also tend to have more white markings on their pronotum than most native North American species.
Asian lady beetles notably aggregate in large numbers, especially in fall, seeking sheltered overwintering locations. They are attracted to sunny, south or west-facing building walls, often mistaking them for natural hibernation sites. Once inside, they release an aggregation pheromone, attracting more individuals.
When disturbed or threatened, these beetles engage in “reflex bleeding,” releasing a foul-smelling, yellowish fluid from their leg joints. This fluid, containing compounds like isopropyl methoxy pyrazine and harmonine, tastes bitter and can stain porous materials like carpets and upholstery. They can also deliver a small, irritating bite, felt as a pinprick.
Ecological Role and Impact
Asian lady beetles play a dual role: beneficial predators with negative impacts. They are voracious predators of soft-bodied insects like aphids, scale insects, and mealybugs, consuming many during larval and adult stages. An adult can consume over 100 aphids daily, making them effective biological control agents in agriculture and gardens. This predatory behavior helps reduce pest populations, lessening the need for chemical pesticides.
Despite beneficial predatory habits, Asian lady beetles are invasive in many introduced regions. Their aggressive nature and high reproductive rate outcompete native ladybug species for food and overwintering sites, contributing to native population decline. Beyond competition, they also prey on other beneficial insects, including native ladybug eggs and larvae. They can carry a microsporidian parasite that doesn’t harm them but can infect and kill other ladybird species, further impacting native populations.
When they invade homes in fall, they become a nuisance pest. Their defensive secretions can stain surfaces and emit an unpleasant odor. Some individuals may experience allergic reactions, including allergic rhinoconjunctivitis, from exposure to these beetles. They can also infest fruit crops like grapes, damaging them and potentially tainting wine flavor if crushed during harvest.
Managing Brown Ladybugs
Managing brown ladybugs, especially Asian lady beetles, focuses on preventing home entry and safely removing those inside. The most effective approach is sealing potential entry points before beetles seek overwintering sites in fall. This involves sealing cracks around windows and doors, utility pipes, and vents with caulk. Repairing damaged window screens and installing tight-fitting door sweeps can also block access. Focusing on sunny, southern and western house sides is important, as these areas attract beetles.
If Asian lady beetles have already entered a home, mechanical removal methods are recommended to avoid activating their defensive secretions. Vacuum cleaners are an effective way to collect them without crushing them and causing stains. It is advisable to empty the vacuum bag promptly after use to prevent the beetles from escaping. Sweeping them into a dustpan for outdoor release is another option, though there is a higher risk of staining.
Insecticides are not recommended for indoor use against these beetles, as they can be ineffective, stain surfaces, and pose risks. For persistent or severe infestations, consulting a pest management professional might be appropriate.