Ladybugs, also known as lady beetles or ladybirds, are dome-shaped insects that constitute the family Coccinellidae. Although their name bears the term ‘bug,’ they are not true bugs (order Hemiptera) and instead belong to Coleoptera, the order comprising beetles. These insects are easily recognized by their bright body colors, often marked with spots and markings, which they use as a potential warning to ward off predators.
Around 6,000 species of ladybugs are found across the globe, except in the polar regions. Most species are carnivorous, preying on aphids and scale insects, which makes them important biological control agents in agriculture.
These insects typically range between 0.03 and 0.7 in (0.8 and 18 mm). The adult females tend to be slightly larger than their male counterparts.
Their bodies have notable dome-shaped backs and flattened undersides. The body is divided into three broad segments (tripartite arrangement): head, thorax, and abdomen.
The head bears a pair of large compound eyes and clubbed antennae with 7 to 11 segments. The mouthparts are chewing or mandibulate type, used for crushing soft-bodied prey.
The thorax is subdivided into pro-, meso, and metathoracic regions, each bearing a pair of legs. The prothorax is covered by a hard, dorsal, shield-like plate called the pronotum. Next to the pronotum lies the mesothorax, which bears the second pair of legs and the first pair of wings, which are modified into hard wing covers or elytra. The metathorax bears the third pair of legs and the second pair of membranous wings, which are actually used for flight.
In most species, the abdomen typically has 10 visible segments. However, the first few segments are partly hidden under the elytra. The abdominal region bears the respiratory, digestive, excretory, and reproductive systems. In adult females, the last few abdominal segments are modified to form the egg-laying organ or ovipositor.
Due to the presence of pigments in the cuticle, particularly the elytra, ladybugs are vibrantly colored. While carotenoids confer lighter base colors, such as yellow, orange, and red, melanins add darker shades, such as brown and black, in the form of spots, stripes, or other markings.
The term Coccinellidae, coined by Pierre André Latreille in 1807, derives from the Latin word coccineus, which translates to ‘scarlet’. The taxonomy stems from the scarlet-red elytra of the most commonly observed species, the common ladybug (Coccinella septempunctata).
Around 6,000 species of ladybugs are classified into 7 subfamilies.
Although fossil records of this group are scarce, the oldest members, dating back to the Early Eocene Epoch, have been derived from amber deposits of Oise and the Bay of Gdańsk, France.[1]
These beetles are found on all continents except Antarctica, with their highest diversity in the tropical region. Most species inhabit tropical rainforests, where they occupy both the forest floor and the upper canopy of the trees. However, a few species, such as the racing stripe darkling beetle (Stenocara gracilipes), are found in deserts. Some groups, including whirligig beetles (family Gyrinidae), squeak beetles (family Hygrobiidae), and skiff beetles (family Hydroscaphidae), are aquatic during all stages of their life.[2]
They are primarily carnivorous insects that feed on soft-bodied insects. Around 36% of the total number of ladybug species consume scale insects, while 68% of temperate species eat aphids. Other insects eaten by ladybugs include whiteflies, psyllids, and adelgids.[3] However, some species, like the large leaf-eating ladybug (Papuaepilachna guttatopustulata), are herbivorous and typically feed on leaves.
When the primary prey is scarce, ladybugs switch to a secondary diet comprising leaves, pollen, honeydew, nectar, and sap. Some species, such as the fungus-eating ladybird (Illeis galbula), feed on powdery mildew fungi that grow on cucurbit crops.[4]
These beetles are diurnal, flying around during the day. They typically cover short distances for foraging, though a few species have been observed taking true long-distance flights. For instance, the convergent lady beetle (Hippodamia convergens) migrates seasonally from overwintering sites in the mountains to agricultural fields over kilometers. In the laboratory, this species has been observed to fly continuously over 20 km.[5]
Their primary line of defense is their bright body coloration, which serves as a visual warning to predators. These colors indicate that these insects might be toxic or unpalatable.
When threatened, most ladybugs exude bitter, foul-smelling hemolymph from their knee joints (reflex bleeding). Their hemolymph contains toxic alkaloids, azamacrolides, polyamines, and pyrazines, which help deter the predators. Additionally, many species, including the common ladybug, pull in their legs, fold their antennae, and remain motionless, pretending to be a dead insect (thanatosis).[6][7]
On average, ladybugs survive up to a year in the wild. They can live without food for up to 9 months.[8]
In the tropics, ladybugs reproduce during the monsoon, whereas in the temperate regions, they reproduce in spring or early summer. They are promiscuous, meaning both males and females have multiple sexual partners throughout their lives. The male transfers packets of sperm (spermatophore) to the female during mating. In the common ladybug, the male inserts up to three spermatophores in the female’s body, each comprising around 14,000 sperm.[9] The female stores the received sperm in the sperm-storing organ (spermatheca), which is then used for fertilizing the eggs internally.
Like most other insects, ladybugs undergo holometabolous (complete) metamorphosis, where the egg undergoes larval and pupal stages before becoming adults. The female lays 10 to 50 bright yellow eggs, which then hatch into tiny black larvae in 4 to 8 days. The larvae undergo three molts in about 3 weeks and eventually transform into pupae. At this stage, the pupae stop feeding, become immobile, and develop an outer, protective case.
In 5 to 7 days, the adult emerges from the pupal case. It pumps hemolymph into its wings and elytra to expand them. The wings eventually harden, and the ladybug attains sexual maturity in a few days to weeks.
These insects are preyed upon by a wide range of predators. For example, some birds, like swallows, swifts, and crows, eat ladybugs when other food sources are scarce. Similarly, some web-weaving spiders accidentally trap these beetles. Frogs and lizards may also consume ladybugs, especially when they mistake them for other small insects.
Other insects, such as lacewings and ants, may attack ladybugs for defensive purposes.
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