, DOI: 10.1111/j.1365-3113.2006.00337.x A revision of the spring-tail genus Vesicephalus Richards (Collembola, Symphypleona, Sminthurinae) ENRIQUE BAQUERO 1 , RICHARD SNIDER 2 and RAFAEL JORDANA 1 1 Department of Zoology and Ecology, University of Navarra, Pamplona, Navarra, Spain and 2 Department of Zoology, Michigan State University, E. Lansing, Michigan, U.S.A. Abstract. 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. Introduction In 1956, Richards described the genus Vesicephalus in his unpublished PhD dissertation. Delamare Deboutteville & Massoud (1964) validly published the name in a revision of the genus and placed it in the subfamily Vesicephalinae Richards in Delamare Deboutteville & Massoud, 1964. The genus currently includes Vesicephalus longisetis (Guthrie, 1903) (Fig. 1a), Vesicephalus occidentalis (Mills, 1935) (Fig. 1b) and Vesicephalus crossleyi Snider, 1985 from North America, Vesicephalus europaeus Ardanaz & Pozo, 1985 (Fig. 1c, d) from the northern Iberian Peninsula and Vesicephalus bellingeri Bretfeld, 2002 (Fig. 1e, f) from eastern Russia (Fig. 2). Richards (1968) listed another, undescribed American species (Vesicephalus sp.), that we have been unable to find, and Richards gave no informa- tion about its distribution. Whilst taking samples for the project ‘Fauna Iberica’, live specimens of V. europaeus were captured. This species had been described in 1985 from only three specimens captured in pitfall traps from northern Spain. Our new specimens allowed an in-depth morphological study by optical microscopy and scanning electron microscopy (SEM), and enabled a more detailed redescription of the species. This new description, which modified the original, led us to believe that descriptions of the North American species could also be incomplete. Therefore, we examined type material from different museums by light microscopy. In the case of V. crossleyi, from the Department of Entomology at Michigan State University, we also prepared a male paratype for SEM observation. Materials and methods Material is deposited in the following collections: MSU, Michigan State University, Zoology Department; UMN, University of Minnesota, Department of Entomology; INHS, Illinois Natural History Survey, University of Illinois; MZNA, Museo de Zoologı´a, Universidad de Navarra, Spain; Bretfeld personal collection, Zoological Institute, University of Kiel. Olshausenstrasse 40, D-24098 Kiel, Germany. Specimens of V. europaeus selected for this study were separated from leaf litter using Berlese–Tullgren funnels. Preparation for SEM was performed using a 2 : 2 : 1 mix- ture of methanol, acetic acid and water for fixation (Saito & Osakabe, 1992), critical point drying with CO 2 and gold Correspondence: Enrique Baquero, Department of Zoology and Ecology, University of Navarra, PO Box 177, 31080 Pamplona, Navarra, Spain. E-mail: ebaquero@unav.es Systematic Entomology (2006) 31, 633–647 # 2006 The Authors Journal compilation # 2006 The Royal Entomological Society 633