PLECTROTAXY OF CENTIPEDES—CRABILL 401 
until Broelemann published his monograph on the French chilopod 
fauna in 1930, at which time he incorporated the Ribaut formulae in 
the description of each species. Unfortunately, even this impetus, 
expertly and extensively utilized in a work of paramount importance, 
was insufficient to attract contemporary interest. 
nee pretarsus 
tarsus 2---- 
tarsus 1--- 
DTiA------ 
Figure 1.—Tenth leg of Lithobius tibia peSess 
forficatus (Linné). Dorsal aspect, 
setae deleted, spurs solid in black. 
Leg articles, lower-case letters; leg DFA A No) wae DFP 
spurs, upper-case letters. 
trochanter ---- 
The Ribaut System and Subsequent Useful Modifications 
Examining again the dorsal surface of the tenth prefemur of Z. 
forficatus, we see that one of the three spurs is situated just cephalad 
of the dorsal prefemoral condyle, a second spur is located just caudad 
of the condyle, and the third spur arises from the extreme caudal 
surface of the article. This arrangement is typical of spurs on any leg 
article: it includes all the spurs that usually occur on one side. It is 
an arrangement that undergoes modification in various other species, 
almost always by depletion, or, in a very few forms, by the addition 
of supernumerary spurs on the last one or two pairs of legs. Ribaut 
