THE PSEUDOSCORPIONS OF CALIFORNIA 



NATHAN BANKS 

 U. S. DEPT. AGRICULTURE, WASHINGTON, D. C. 



The Pseudoscorpions are a very strongly circumscribed group of the Arach- 

 nida. Of the general appearance of diminutive scorpions they differ in so many 

 important structures as to be far removed from tlum in the system. They lack 

 the post-abdomen or "tail" of the scorpions, and consequently the sting; they have 

 no median pair of eyes, no sternum, no pectines, and there are various differences 

 in the legs and mandibles. The scorpions have four jiairs of stigmal orifices on the 

 venter of the abdomen, whereas the pseudoscorpions have but two pairs of stigmata. 

 Practically all authors put them in an order by themselves, variously called 

 Chelonethi, Chernetidea or Pseudoscorpionida. Their relationships are considered 

 to be closer to the Phalangida and Acari than to the scorpions. The body of a 

 Pseudoscorpion, or Chclifer, is seen to be of two principal parts, a large front 

 part, not or only indistinctly segmented, the cephalothorax ; and a segmented 

 posterior part, broadly attached to the cephalothorax, the abdomen. Attached to 

 the front of the cephalothorax are the mandibles, chelicera? (or antennae of some 

 authors), and a pair of long palpi ending in a large claw, these are the pedipalpi. 

 The legs are attached to the under surface of the cephalothorax, their coxae being 

 approximated. The dorsal surface of the cephalothorax often bears on each 

 anterior side one or two eye-spots, but there are a number of eyeless species. In 

 some forms there are one or two transverse furrows or grooves on the cephalo- 

 thorax, and the surface is often granulated or roughened. 



The mandibles, or chelicerae, are rather small, but in some forms large and 

 conspicuous; they are of two joints, a large basal joint called the hand, or paturon, 

 and a slender, curved apical joint or finger; the tip of the paturon is prolonged 

 in a process of similar size and shape to the apical joint, the two fingers forming 

 a claw. The apical joint is called the movable finger, and the other the immovable 

 finger of the mandibles. The basal joint often bears a more or less branched 

 process, the flagellum ; while the movable finger often has a comb-shaped process 

 attached more or less closely to its inner edge ; this is the serrula. The movable 

 finger bears an apical process, sometimes reduced to a tubercle, but usually slender, 

 called the galea, or stylet; this contains the aperture of the silk glands, which are 

 situated in the cephalothorax. The structure of these parts is of great value in 

 classification. The pedipalpi consist of six joints; the basal is the coxa; then 

 follow trochanter, femur, tibia, and the hand ending in two curved fingers which 

 form a claw; one finger is movable, the other but an extension of the previous 

 joint. Each leg is composed of a coxa, trochanter, femur (usually divided), tibia 

 and a tarsus of one or two joints. The femur usually shows at its base a triangular 

 part cut off by a suture from the main portion. This basal piece is the trochantin. 

 In some species it is so distinctly separated from the femur as to appear as a 

 separate joint. The tarsi end in a pair of simple claws, and in some cases a 

 membraneous ambulacrum, or arolium. 



