Are Ladybugs Poisonous? Bright Colors and Reflex Bleeding

What makes ladybugs poisonous?

Ladybugs are beetles of the family Coccinellidae, and most of them carry a chemical defense in their blood. The main ingredients are alkaloids, nitrogen-containing compounds that taste bitter and can be toxic to small predators. Ladybirds as a group produce at least 50 different alkaloids, and each species has its own mixture. The seven-spot ladybug relies mainly on coccinelline and precoccinelline, the two-spot ladybird on adaline and the harlequin ladybird on harmonine.

Unlike many poisonous insects, ladybirds make these chemicals in their own bodies rather than taking them from food. A monarch caterpillar, by contrast, stores toxins from the milkweed it eats, as explained in are monarch butterflies poisonous? Ladybirds also produce pyrazines, strong-smelling compounds that give their fluid its distinctive musty odor.

It helps to separate two words. A venomous animal injects toxins with fangs, spines or a stinger. A poisonous animal is harmful only when another animal bites, swallows or sometimes touches it. Ladybugs are poisonous in this sense, but they are not venomous.

What is reflex bleeding?

When a ladybug is pecked, squeezed or grabbed, it can squeeze drops of yellow to orange fluid out of the joints between the thigh and shin of its legs, its “knees”. This fluid is the beetle’s blood, called hemolymph, and it carries the bitter alkaloids and pungent pyrazines. Biologists call the behavior reflex bleeding or autohemorrhaging.

To a bird, an ant or a spider, the effect is like biting into something both foul-smelling and bitter. The predator usually drops the beetle at once, and the ladybug often survives. Reflex bleeding is not free, though: the beetle loses body fluid that it must replace, so it saves the response for real threats.

Ladybugs have a second trick. When disturbed, many pull their legs and antennae tight under the body and play dead. A predator looking for moving prey may lose interest, and the tucked-in legs are protected under the hard shell.

How do warning colors work?

Bright colors that advertise a defense are called aposematic, or warning, colors. Red, orange and yellow combined with black are common warning patterns in nature because they stand out against green leaves and are easy for predators to remember. A young bird that tastes one ladybug learns quickly to avoid others that look similar.

Research suggests the warning is honest. A 2015 study of five ladybird species found that the species and individuals that stood out most against their background tended to be the most toxic. In the seven-spot, the color of the wing cases has also been linked to how much defensive chemical a beetle carries.

The same principle explains the vivid colors of many other poisonous animals, from poison dart frogs to some caterpillars, as described in why poison dart frogs are colorful. Some harmless animals cheat. Males of the ladybird spiders (genus Eresus) of Europe have red backs with black spots, a disguise that may help protect them from birds even though they lack the ladybird’s chemicals.

Does anything eat ladybugs?

Because of their chemical defense, adult ladybugs have few regular enemies. Some birds, spiders and insects still eat them, and certain checkered beetles (genus Enoclerus) in North America prey on ladybugs despite their toxins. Ladybug eggs, larvae and pupae are more vulnerable, and lacewing larvae and other ladybirds eat many of them.

Ladybirds also poison each other. The harlequin ladybird eats the eggs and larvae of native species, but its own eggs contain harmonine, which is toxic to many native ladybirds that try to eat them. This chemical edge is one reason the harlequin has spread so successfully in Europe and North America.

Can ladybugs harm people?

For people, ladybugs are harmless. They have no venom and cannot sting. A ladybug may occasionally nip skin, especially the harlequin ladybird, but the bite is a tiny pinch. During the enormous 1976 swarm of seven-spot ladybirds in England, many people reported nips from beetles that were probably looking for moisture in the hot, dry weather.

The real nuisances are smaller. Reflex fluid can leave yellow stains on skin, clothes and curtains, and it smells unpleasant. In homes where harlequin ladybirds gather for the winter, a small number of people develop allergy symptoms such as sneezing, a runny nose or itchy eyes. Anyone who has a severe allergic reaction should seek emergency medical help immediately (call 911 in the US, 112 in the EU or 999 in the UK).

The strength of ladybird chemicals shows up in an unexpected place: wine. When harlequin or seven-spot ladybirds are crushed with grapes, their pyrazines give wine a green, bell pepper or peanut-like flavor called ladybug taint. Studies suggest that as few as about 1.3 to 1.5 beetles per kilogram (2.2 lb) of grapes can affect wine quality.

Are orange ladybugs more poisonous?

Posts online sometimes claim that orange ladybugs are dangerous while red ones are safe. Color alone is not a reliable guide. Many ladybird species come in several colors, and the harlequin ladybird alone can be orange, red or black with anything from no spots to more than twenty.

There is a grain of truth behind the claim. Many orange ladybugs in Europe and North America are harlequins, which carry particularly potent defensive chemicals and are the species most likely to nip people or gather in houses, where they can become a nuisance in autumn, as described in where ladybugs go in winter. But no ladybug, of any color, is dangerous to touch.

Ladybugs are a textbook example of a small animal that is poisonous without being venomous, a defense they share with many creatures in the most poisonous animals, though their toxins are far milder.