A SYNOPSIS OF THE CAVE MILLIPEDS OF 
THE UNITED STATES, 
WITH AN ILLUSTRATED KEY TO GENERA* * 
By William A. Shear 
Museum of Comparative Zoology, Harvard University 
INTRODUCTION 
The taxonomy of the Class Diplopoda is presently in a chaotic 
and undeveloped state, even in an area so well-studied for most 
organisms as the United States. Attempts by the uninitiated to iden- 
tify collections of even the most common forms of millipeds are 
usually thwarted by the lack of keys and revisions in the literature, 
and specialists in this group are frequently swamped with requests 
for determinations from ecologists, museums, general collectors and 
speleobiologists. Cave explorers have made a great contribution to 
our knowledge of the milliped fauna, of the United States, with the 
result that the hypogean forms are usually better known than epigean 
ones. 
At least in the United States, it seems unlikely that additional 
representatives of new families and genera of millipeds will be dis- 
covered in caves, and therefore the time seems ripe for a synopsis 
of our knowledge of troglobitic diplopods. Causey (1960b) sum- 
marized the features characterizing a milliped as a troglobite, though 
all sorts of gradations may be obtained within a given family from 
troglobite through troglophile to cave accidental. In general, pig- 
mentation and the number of ocelli, if these are usually present in 
the family, are reduced in troglobites. The antennae and legs are 
longer in proportion to their thickness than in related epigean spe- 
cies and the body segments themselves may be elongated and nar- 
rowed. Calcification of the cuticle is often reduced. The dorsal 
ornamentation so characteristic of many of the families of millipeds 
is usually suppressed, though in at least one case ( Pseudotremia , 
Cleidogonidae) , some highly cave-adapted species are more orna- 
mented than epigean ones. Troglobitic millipeds are frequently a 
little larger than their epigean relatives, though in some cases ( Pseu- 
dotremia ; Cambala , Cambalidae) troglobites are much smaller. Speo- 
striaria (Striariidae) and Tetracion (Order Callipodida, family 
name uncertain) are the giants of their respective families in North 
Published with the aidi of a grant from the Museum of Comparative 
Zoology. 
*Manuscript received by the editor May 6, 1969 
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