This image is a high-resolution differential interference contrast (DIC) micrograph of a female human flea (Pulex irritans). Fleas bite their hosts causing a skin reaction and a condition known as Pulicosis. Flea bites cause an itching sensation and some people and animals can suffer from an allergic reaction to flea saliva, resulting in a rash. Fleas can also act as a vector for disease, transmitting a variety of viral and bacterial infections. Magnification: 25x. Supplied by David Linstead, courtesy of Wellcome Images.