How do bedbugs look at different developmental stages? - briefly
The immature stages comprise five nymphal instars that grow from about 1 mm to 4 mm, remain wingless, and shift from a pale, translucent hue to a darker reddish‑brown as they develop. The adult measures 5–7 mm, exhibits a flattened oval body, a darkened abdomen, and visible eyespots on the head.
How do bedbugs look at different developmental stages? - in detail
Bedbug development proceeds through egg, five nymphal instars, and the mature adult. Each stage possesses distinctive visual characteristics.
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Egg – Approximately 0.5 mm in length, the egg is spherical to ovoid, smooth, and translucent white. It adheres to surfaces with a sticky secretions, making it difficult to see against light-colored backgrounds.
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First‑instar nymph – Measures 1.2–1.5 mm. The body is translucent with a faint amber tint; legs and antennae are pale and delicate. The dorsal surface lacks the characteristic reddish hue of later stages.
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Second‑instar nymph – Grows to 1.5–1.8 mm. The cuticle darkens slightly, acquiring a light brown coloration. Wing pads remain absent, and the body remains flattened, facilitating movement within crevices.
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Third‑instar nymph – Reaches 1.8–2.1 mm. The dorsal coloration deepens to a medium brown, and the abdomen shows the first hints of the adult’s reddish‑brown tone. Antennae become more pronounced, with four visible segments.
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Fourth‑instar nymph – Size ranges from 2.0–2.4 mm. The body exhibits a uniform reddish‑brown shade, though the edges of the abdomen retain a paler margin. The exoskeleton thickens, providing greater rigidity.
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Fifth‑instar nymph – Approaches adult dimensions at 2.4–2.7 mm. The coloration matches that of the mature insect, with a matte, dark reddish‑brown dorsum. Wing pads remain vestigial, and the insect prepares for the final molt.
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Adult – Length 4.5–5.0 mm, width 1.5–2.0 mm. The adult displays a flattened, oval body, uniformly reddish‑brown to mahogany, with a glossy sheen after feeding. Six legs terminate in small, claw‑like tarsi adapted for grasping fabric fibers. Antennae consist of four segments, each bearing sensory hairs. The proboscis, concealed under the head, extends during blood feeding.
Throughout development, the absence of functional wings persists, and the overall body plan remains dorsoventrally flattened, enabling infiltration of narrow seams and mattress folds. Color transition from translucent to deep reddish‑brown marks the progression toward reproductive maturity.