PALPIGRADI. 



827 



Order 4. PALPIGRADI* 



Arachnids with a cephalothorax (prosoma) of four fused segments 

 corresponding with the 

 first four jointed limbs, 

 and of the 5th and 6th 

 segments which remain 

 free ; the, abdomen 

 (meso- and meta-soma) 

 is stalked and narrowed 

 behind ; it is composed 

 of eleven segments and 

 bears a long multi- 

 segmented appendage ; 

 the chelicerae are 

 three-jointed ; no eyes ; 

 the mouth is bounded 

 by an epistome and a 

 hypostome. 



It is only within 

 the last twenty years 

 that the Palpigradi 

 have been discovered 

 and investigated. 

 They fall into two 

 genera, Prokoenenia 

 and Eukoenenia. They 

 are all minute, their 

 total length being 

 scarcely 1 mm. They 

 are very widely dis- 

 tributed. 



The prosoma con- 

 sists of four fused seg- 

 ments corresponding 

 with the four anterior limbs, viz. the chelicerae, the pedipalpi, 



yrce-l 2 

 II in IV V VI ' gen 

 Prosoma 



34567 8910 

 Opislhosoma 



FIG. 545. Eukoenenia, mirabilis, Grassi, one of the 

 Palpigradi. A ventral view of cephalothorax (pro- 

 soma) and of anterior region of abdomen (opisthosoma) 

 with the appendages cut off near the base : a 

 and b prosternites : c mesosternite ; and d meta- 

 sternite of the prosoma ; / ventral surface of the 

 praegenital somite ; g sternite of the genital somite 

 (first opisthosomatic somite). B dorsal view, I 

 to VI, prosomatic appendages ; 1 opisth, genital 

 somite (first opisthosomatic somite). C lateral view. 

 I to VI prosomatic appendages ; a, b, c the three tergal 

 plates of the prosoma ; praegen, the praegenital somite ; 

 1 to 10, the ten somites of the opisthosoma. D cheli- 

 cera. (Original drawing by Pocock and Pickard- 

 Cambridge, after Hansen and Sorensen.) 



* Grassi, Natural SiciL, iv, 1885, p. 127, and Bull. Soc.ent. ItaL, 1886, 

 xviii, p. 153. Thorell, Ann. Mus. Genova, 1888, xxvi, p. 358 ; and Hansen 

 and Sorensen, Ent. Tidskr., 1897, xviii, p. 223. Augusta Rucker, Q. J. 

 Mic. Sci., xlvii, 1904, p. 215. Also Zool. Jahrb. Morph., 1903 and Amer. 

 Nat., xxxv, 1901, p. 615 ; and Wheeler, Amer. Nat., 1900, p. 837. C. 

 Borrer, Zool. Anz., xxiv, 1901, p. 537. Hansen, Ent. Tidskr., 1901, p. 193 f 



