282 



Arthropoda. 



-tei-mmal joint. The amis is situated in tie membrane between the last and 

 the penultimate somites. Anteriorly, on the ventral surface of the abdomen, 

 just behind the legs, there arises a pair of flattened, unsegmented appendages 

 (the pectines), the posterior edges of which are toothed; theii- significance is 



unknown. Close to them lies the genital 

 aperture; on the broad portion of the 

 abdomen (pre-abdomen) there are also, on 

 the ventral surface, fom- pairs of slit-like 

 stigmata, the openings of the same number 

 of lung-sacs. The Scorpions are fairly- 

 large animals ; they are viviparous, the 

 yoimg ones remain with the parent for the 

 first few weeks, but the latter dies before 

 long. They occur in the tropics and in 

 the wairmer regions of the temperate zones 

 (two species in S. Europe). They remain 

 in one place, feeding upon Insects and 

 Arachnids, which they seize with their 

 chelsB, and kiU by a stab of the sting. 



2. The Pseudoscorpions (genus 

 Chelifer and others) recall at first sight 

 the Scorpions, which they resemble in the 

 structure of the chelicerae and pedipalpi. 

 They differ, however, in many respects. 

 The abdomen consists of eleven somites; 

 its hinder region is not developed as a 

 post-abdomen, and a sting is absent ; f ui-ther, 

 respiration is by tracheae, which open 

 by two pairs of stigmata on the ventral 

 surface of the abdomen. Anteriorly there 

 are one or two eyes on each side of the 

 cephalothorax, but these may sometimes be absent. On the ventral surface 

 of the abdomen, near to the genital pore, is a number of small papiUse, 

 perforated by the aperttu-es of the spinning glands. The ova and the 

 larvae, which are hatched in a very imperfect condition, are cairied about 

 on the ventral surface of the body ; the former are bound together 

 into a mass. The Pseudoscorpions are sma,U ; they live beneath bark, in 

 moss, old books, collections of Insects, and so forth; they feed upon Mites, 

 Book-lice, etc. 



3. The Harvest Men (Phalangiidse)* have a short, arched body, which is not 

 sharply divided into cephalothorax and abdomen. The cephalothorax, which 

 consists of three indistinct and immovably connected segments, bears a pair of 

 eyes dorsally, like the two median eyes of Scoi-pions ; the chelicerse have small 

 chelae, the pedipalpi are antenniform, much shorter than the extremely long legs, 

 which aa-e characterised by the division of the proximal joint into a number of 

 smaller segments. The abdomen consists of eight iU-defined segments, it is 

 provided, anteriorly, with a pan- of stigmata leading into a system of tracheae. 

 The Phalangiidae are peculiar in that the males possess a long extensile copulatory 

 organ, the females a long eversible ovipositor ; the genital aperture is anterior. 

 At first sight they look veiy Uke long-legged Spiders, and ai-e chiefly met with in 

 the dwellings of mankind. 



Fig. 230. Scorpion, seen ven- 

 trally; cheliceras, legs and post- 

 abdomen not completely drawn, g 

 genital aperture, fc peotines, o ohelioeraa, 

 u pedipalpi, s stigmata, 1 — i legs. — 

 After M. Edwards. 



* This description does not apply to a, few aberrant forms. 



