The short answer is: some ladybugs are more poisonous than others but they don’t cause serious harm to humans or pets.
Ladybugs are beneficial insects that can eat garden pests and reduce pesticide use. While they do have some defensive mechanisms, they aren’t designed to cause serious harm to humans or pets. Studies have shown that black, orange, red, yellow, and spotted ladybugs are poisonous. However, most species haven’t been tested for toxins so there could be many other colors of lady beetles that are also poisonous.
By inbetweenbays, inaturalist.org
These little critters can also cause allergies when they enter your home in large numbers. There are some scary stories out there about them causing harm but, in this article, we will separate the facts from the myths for you.
1. Fact: Some Ladybugs Are Poisonous
Many poisonous animals use aposematic coloration, such as red, orange, yellow, and black, to warn predators they are dangerous. Ladybugs are one example and their red body with black spots is meant to indicate that they are toxic.
These insects can reflex bleed to deter predators. When scared or threatened, they will excrete their hemolymph (blood) from the joints between the leg segments. It is yellow to orange in color, can stain light-colored surfaces, and has a foul taste and smells to deter predators.
By Sam Kieschnick, inaturalist.org
Some coccinellid beetles have alkaloids in their hemolymph which are toxic when ingested. Some of the known alkaloids produced by these critters are coccinelline, adaline, harmonine, exochomine, and propyleine[1].
Research is ongoing regarding the toxicity of ladybug alkaloids and their variability among species. However, it has been confirmed that they are poisonous and that the amount of poison they contain can vary greatly by species[4].
2. Fact: Ladybug Toxins May Cause Tissue Damage
The only reported serious reaction to the toxins from these beetles was in a dog in 2008[5]. The report states that the dog did suffer chemical-like burns in its mouth after ingesting more than a dozen ladybugs. However, the article also notes that the dog was taking an oral medication which may have caused a rare interaction between the medicine and beetle toxins[5].
By Olivia, inaturalist.org
No severe reaction to this little critter has ever been reported in humans or cats. However, there have been rare reports of humans having mild skin irritation or rash after coming into contact with reflex blood or being bitten by a ladybug.
3. Myth: Ladybug Toxins Are Deadly To Humans And Pets
The toxins some species produce can be deadly to birds, reptiles, or small mammals if eaten in large quantities. However, most animals will only eat a few ladybugs due to how terrible they taste and smell.
By Katja Schulz, inaturalist.org
There are no recorded deaths in humans or pets from ladybugs. Humans, cats, and dogs, would need to ingest hundreds or thousands of them for their toxins to result in death. At most, a dog or cat might suffer some digestive discomfort after consuming a few of these beetles.
4. Fact: Some Ladybugs Are More Poisonous Than Others
Several studies have shown that some ladybugs are more toxic than others and that their toxicity can be correlated to their aposematic coloration. For example, Maria et al. (2015) found that orange ladybugs (Halyzia sedecimguttata) were the most toxic, and cream-colored ladybugs without spots (Aphidecta obliterata) were the least toxic species. They also showed that both color variations of the 2-spotted ladybird (Adalia bipunctata) were equally toxic[4].
The table below summarizes the findings of this study and ranks the species tested from most to least toxic.
Other studies have shown the opposite to be true. Marples et al. (1989) tested the toxicity of two species, both with red wings and black spots, on birds. He found that one was much more toxic than the other. This would suggest that color alone can not be used to determine how toxic a species may be.
These findings show that ladybugs with a variety of color combinations can be poisonous including orange, red, black, and yellow. There are more than 6000 species of lady beetle, most of which have not been studied regarding their toxicity. Therefore it would be difficult to say, with certainty, that any color or pattern means a ladybug isn’t poisonous.
Mimicry is likely a part of the puzzle when it comes to using color to predict toxicity in ladybugs. Mimicry is a defensive technique used by many insects which have evolved to look like other species to deter predators. One example of an insect using mimicry is the hover fly which resembles bees or wasps to scare away predators.
By jbartlett79, inaturalist.org
Some red ladybugs may just be using mimicry to trick predators into thinking they are poisonous. This benefits the individual because toxins cost energy to produce. Species using mimicry enjoy the benefits of scaring predators away without having to exert energy to produce toxins.
Research about the relationship between toxicity and coloration in lady beetles is ongoing. While we know that certain species are more toxic than others, there is still some debate about the relationship toxins have with color.
5. Fact: Ladybugs Can Cause Allergies
The allergies these beetles can cause are probably the most ‘dangerous’ effect they can have on humans. Like many indoor insect pests, including cockroaches and dust mites, ladybugs can induce a variety of allergic reactions in certain people when they seek shelter inside for the winter[2].
The multicolored Asian lady beetle is the primary culprit of ladybug-induced allergies since they are the only known species to infest homes in large numbers. Fortunately, ladybugs are not persistent in homes year-round like cockroaches and dust mites. They generally leave houses in spring or die during the winter.
By Vasyliuk Oleksij, inaturalist.org
Unlike dust mites, who spread, multiply, and leave their allergens throughout the home, the allergens from ladybugs are easily removed. They tend to congregate in one area of the home and allergy symptoms quickly disappear after they are removed[2].
Summary
Now that you know the facts and myths about ladybugs, you should feel more at ease about them not causing serious harm to you or your pets. As long as you don’t pick them up, ingest tons of them, and clean them up when you find them inside, they shouldn’t pose any danger to you.
These are great insects to have in your garden because they consume a lot of different garden pests. Now you can rest assured that they aren’t a danger but rather a friend when you find them wandering around outside.
References
[1] Glisan King, A., & Meinwald, J. (1996). Review of the defensive chemistry of coccinellids. Chemical Reviews, 96(3), 1105-1122.
[2] Goetz, D.W., 2008, March. Harmonia axyridis ladybug invasion and allergy. In Allergy & Asthma Proceedings (Vol. 29, No. 2).
[3] María Arenas, L., Walter, D. and Stevens, M., 2015. Signal honesty and predation risk among a closely related group of aposematic species. Scientific Reports, 5(1), pp.1-12.
[4] Marples, N. M., Brakefield, P. M., & Cowie, R. J. (1989). Differences between the 7‐spot and 2‐spot ladybird beetles (Coccinellidae) in their toxic effects on a bird predator. Ecological Entomology, 14(1), 79-84.
[5] Stocks, I. C., & Lindsey, D. E. (2008). Acute corrosion of the oral mucosa in a dog due to ingestion of multicolored Asian lady beetles (Harmonia axyridis: Coccinellidae). Toxicon, 52(2), 389-391.
