with pederin, a vesicant toxin in the hemolymph of many but not all females in the genus Paederus. The toxin is manufactured, not by the beetles themselves, but by endosymbiont bacteria, probably some species of Pseudomonas. Impact on human beings Paederus dermatitis is caused when a pederin-containing beetle is crushed, even partially, against the skin. This skin irritation is also called "dermatitis linearis" or "linear dermatitis" because one can inadvertently drag a beetle across the skin in a more-or-less straight line when trying to brush it away. The resulting inflammation will also be linear. Because Paederus species are widely dispersed around the world, this syndrome has many different local nicknames including "whiplash dermatitis", "spider lick", and "Nairobi fly dermatitis". In East Africa, conjunctivitis from getting pederin in the eye is called "Nairobi eye". Once pederin is on the skin from the initial beetle contact, it may also be spread elsewhere on the skin. "Kissing" or "mirror-image" lesions where two skin areas come in contact (for example, the elbow flexure) are often seen. Washing the hands and skin with soap and water is strongly recommended if contact with a rove beetle has occurred. Initial skin contact with pederin shows no immediate result. Within 12–36 hours, however, a reddish rash (erythema) appears, which develops into blisters. Irritation, including crusting and scaling, may last from two to three weeks. Mass infestations An article in The Lancet suggests that events like those described as the first two of the ten plagues of Egypt (anoxic die-off in the Nile, followed by many dead frogs) would have created ideal breeding conditions for P. alfierii. The authors suggest that the plague of "boils" could be the skin irritation, typically delayed by a day or more, resulting from contact with Paederus during the third or fourth plagues (lice or flies). They also note that Paederus infestations are often localized, so it would be quite possible for them to have invaded Pharaoh's palace but not the homes of the Jews. Many modern occurrences of localized but intense Paederus impact are documented in research papers with titles like "An outbreak of paederus dermatitis in a suburban hospital in Sri Lanka", "An outbreak of 268 cases of Paederus dermatitis in a toy-building factory in central China", "Outbreak of dermatitis linearis caused by Paederus ilsae and Paederus iliensis (Coleoptera: Staphylinidae) at a military base in Iraq", and "Evacuation of an Aboriginal community