Description of the Postlarval Stages of Dactylochelifer gracilis Beier, Pseudoscorpiones: Cheliferidae

A study of the free-living developmental stages of Dactylochelifer gracilis Beier, 1951, is presented based on 68 specimens of all nymphal and adult stages, collected from two locations in Iran. Basic differences of all stages are characterized by size, pedipalpal ratios, and the addition of trichobothria and setae during development. 1. Introduction Pseudoscorpions are small arachnids usually 2–8？mm in length (e.g., [1]). They are generally confined to habitats such as leaf litter, under stones, under trees or log barks, bird’s nests, and mammal’s lairs (e.g., [2]). Their life cycle is ovo-viviparous and consists of four phases (e.g., [3]): (1) eggs which are attached to the female’s abdomen and carried by her in a brood sac, (2) two larval instars that also remain in the brood sac, (3) three nymphal instars, and (4) adults. Nymphs are very similar to adults but are smaller (Figures 8, 9, and 10) and lack genital organs (Figure 11). The three nymphal instars are termed protonymph, deutonymph, and tritonymph and can be easily recognized by the unique number of trichobothria of each stage [4]. In addition to the differences in the sexual organs, adult females are generally slightly larger than males. The present study is focused on the external morphology of the postlarval stages of a species of Dactylochelifer Beier from Iran. This genus is a member of the family Cheliferidae [5, 6], which belongs to the Cheliferoidea along with Atemnidae, Chernetidae, and Withiidae [7, 8]. Dactylochelifer is widely distributed in the Holarctic region [6] and can be recognized by the following combination of features: presence of coxal sacs situated within the coxae of the fourth pair of legs of males, each sac with a well-developed atrium (Figure 7(a)); tarsus with simple subterminal seta (Figures 7(c) and 7(d)); presence of a median seta on each half tergite; tarsal claws not divided; and female with one cribriform plate (Figure 11(e)) [9]. The first pseudoscorpion reported from Iran, Chelifer spinipalpis Redikorezev, 1918, now placed in the genus Strobilochelifer, was described from Bazman, Southeastern Iran [10]. The most substantial contributions were by Beier [11, 12]. There are currently nine families, 21 genera, and 39 species known from the country [6]. There are currently 44 species belonging to the genus Dactylochelifer of which 28 are represented in the Middle East and Central Asia [6]. Although many Asian species are poorly known with brief published descriptions and few illustrations, recent revisionary work on the Central Asian fauna (e.g., [9, 13]) has