This excitatory toxin inhibits insect calcium-activated potassium (KCa) channels (Slo-type). Pan-neuronal expression in Drosophila is lethal but flies engineered to express the toxin only in clock neurons have defects in circadian rhythm but a normal lifespan. Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. LD(50) of recombinant toxin is 320 +-20 pmol/g in house flies (Musca domestica). LD(50) of recombinant toxin is 91 +-5 pmol/g in house flies (Musca domestica). Does not affect a wide range of potassium, calcium and sodium voltage-gated channels. Belongs to the neurotoxin 11 (kappa toxin) family. This toxin has the prefix lambda in its name (instead of kappa), since lambda is the Greek letter attributed to calcium-activated potassium (KCa) channel impairing toxins (according to the nomenclature of King et al., 2008).