254 
Psyche 
[December 
Burrowing consisted of repeated irregular sequences of biting- 
raking, biting-raking, biting-raking-plowing or raking, raking, rak- 
ing-plowing. The sequence was continued even after the burrow 
was plugged and the solpugid’s digging was entirely subterranean. 
The only consistent variation occurred when obstructions such as 
pebbles, fragments of wood, etc., were encountered. These were 
bitten free and carried out of the way with the chelicerae. Some 
species also exhibited two palpal activities : probing, in which the 
palpi lightly touched unexcavated soil, and tamping, in which the 
palpi tapped or pushed excavated soil. 
1 he three principal burrowing operations were analyzed. Biting 
involved both alternate and simultaneous use of the chelicerae. Bur- 
rows in hard, firmly packed soil were started by biting while angling, 
turning, and twisting the propeltidium and chelicerae, or by rotating 
the entire body around the area being bitten. Raking was accom- 
plished with the laterodorsal row of spines on the tibiae of the sec- 
ond and third legs. The third leg was not used consistently. During 
raking, the legs were twisted inward and pulled backward quickly 
either in unison or alternately which hurled the sand and particles 
of clay backward under the body between the fourth pair of legs. 
Vigorous raking cast excavated material up to 5 cms behind the solpu- 
gid’s body. When loose sand and clay accumulated under or just 
behind a burrowing solpugid, it turned around and plowed the pile 
out of the way. Plowing involved a lowering of the body to place 
the chelicerae at or near the base of the pile, the palpi and first legs 
were flexed at each side of the pile seemingly to prevent lateral scat- 
ter, and the pile was pushed as with a bulldozer, or road-grader. 
Plowing deposited moist excavated material in piles up to 10 cm from 
the burrow entrance ; dry excavated material was scattered and 
leveled ( Fig. 1 ) . 
Position reversal in the burrow, not previously reported, was 
accomplished as follows. The propeltidium was bent to the side or 
upward and backward over the meso- and metapeltidia and the palpi 
and legs were folded laterally along the sides of the abdomen. The 
solpugid then walked backward on the burrow side or ceiling which 
caused the peltidia and abdominal somites to undergo a backward 
rolling fold until the animal had completely reversed its position. 
The solpugid then twisted into an upright position completing posi- 
tion reversal. Position reversals were necessary for plowing, espe- 
cially when the burrow was one or more body lengths long. 
When the burrow was one or more body lengths long, the solpugid 
plowed only to the entrance (Fig. 3) which closed or plugged the 
