CHAP. XVI PALPIGRADI—SOLIFUGAE 423 
genital operculum is complicated, and is situated beneath the 
second abdominal segment. 
Since 1885 several other species have been discovered in 
various parts of the world. Two American ‘ 
forms possess three pairs of lung-sacs on Ni Y, 
segments 4, 5, and 6 of the abdomen. 
Rucker’ has suggested for them the 
generic name of Prokoenenia, including 
P. wheeleri, Rucker, from Texas, and P. 
chilensis, Hansen, from Chili. The others, 
styled by that author Hukoenenia, have 
no lung-sacs. There are about ten GF A 
species, mostly from the Mediterranean ram peek 
= \ 
region, but HL. augusta, Hansen, is found 
in Siam, /. florenciae, Rucker, in Texas, ae 
and £. grassii, Hansen, in Paraguay. 
NE 
Order V. Solifugae (Solpugae). fi 
fi 
: ye 
Tracheate Arachnids, with the last three iA 
segments of the cephalothorax free and the 
abdomen segmented. The chelicerae are 
largely developed and chelate, and the 
pedipalpy are leg-like, possessing terminal 
SENSe-OTYANS. 
The Solifugae are, in some respects, Fic. 216.— Koenenia mira- 
the most primitive of the  tracheate ree aes enlarged. 
Arachnida. Their general appearance is 
very spider-like, and by the old writers they are uniformly 
alluded to as spiders. The segmented body and the absence of 
spinning organs, however, make them readily distinguishable on 
careful inspection. They are for the most part nocturnal 
creatures, though some seem to rove about by day, and are even 
called “Sun-spiders” by the Spaniards. The night-loving species 
are attracted by light. They are, as a rule, exceedingly hairy. 
Some are extremely active, while the short-legged forms (e.g. 
Rhagodes, see p. 429) move slowly. They are capable of pro- 
ducing a hissing sound by the rubbing together of their chelicerae. 
Only the last three pairs of legs are true ambulatory organs, the 
1 Quart. J. Micr. Sct. xlvii., 1904, p. 215. 
