LD

Definition

Abbreviation for lethal dose; the amount of a toxin, venom, or chemical required to kill a specified percentage of a test population under controlled conditions. Typically expressed as LD₅₀ (dose lethal to 50% of subjects), with lower subscripts indicating higher toxicity. In arthropod research, LD values standardize comparisons among venoms, insecticides, and resistance mechanisms across species, life stages, and exposure routes.

Etymology

Initialism of English 'lethal dose', established in toxicology literature by the mid-20th century.

Example

The LD₅₀ of black widow spider (Latrodectus hesperus) venom in mice is approximately 0.9 mg/kg when administered intravenously, but drops to 0.003 mg/kg when injected intracerebrally, illustrating how route of exposure dramatically alters apparent toxicity.

Synonyms

• lethal dose

Related Terms

• LC
• ED
• Toxicity
• dose-response
• venom
• insecticide resistance
• toxicology
• LD₅₀

Usage Notes

Always subscripted with the percentage killed (LD₅₀, LD₉₀, LD₁₀₀). Distinct from LC (lethal concentration) for airborne or aquatic exposures. In entomology, LD values are critical for comparing susceptibility among field populations, detecting resistance evolution, and registering new insecticides. Venom LD values vary enormously with injection site, animal model, and test conditions; interspecific comparisons require standardized protocols.