A revision of the spring-tail genus Vesicephalus Richards (Collembola, Symphypleona, Sminthurinae).

A detailed morphological study of the collembolan genus Vesicephalus Richards in Delamare Deboutteville & Massoud, 1964 is presented, with the redescription of known species on the basis of new scanning electron microscopy observations. Vesicephalus is a rare genus found in North America, Spain (Europe) and Russia, having the unique characteristic of a pair of interocular vesicles with demonstrated photoreception function. This feature may be responsible for habitat restriction within the species range. The possible function of this photoreceptor is high sensitivity to light, which permits these animals to live in a dark environment. A key to the known five species is presented, together with chaetotaxic illustrations