Centipede Subfamily Plutoniuminae 55 



that modern myriapod taxonomy be soundly based and not recapitulate 

 this heritage, and the ultimate, and often penultimate, legs hold taxonomic 

 importance in many scolopendromorph genera. The erection of new 

 genera for anatomically incomplete chilopods, taxa that future workers 

 will be compelled to reconceptualize, cannot be too strongly discouraged. 



Another intriguing aspect of Theatops is the nearly identical external 

 structures of T. erythrocephalus, in Europe, and T californiensis Chamberlin, 

 in California and Oregon, which are separated by around 11,520 km 

 (7,200 mi). This resemblance was interpreted as convergence by Shelley 

 (1990a), and it has produced especially similar external anatomies; 

 the species are so nearly identical that confusion reigned for 88 years 

 over the correct name for the latter. Past authors labeled it T californiensis 

 (Chamberlin 1902), T erythrocephalus californiensis (Chamberlin 1911), 

 and T. erythrocephala (Attems 1930, Chamberlin 1951a). Crabill (1960) 

 and Kevan (1983) called it T. californiensis but suggested synonymy 

 with T. erythrocephala. This enigma was resolved by Shelley (1990a), 

 who deduced from variation in southwestern forms of T. posticus that 

 T californiensis is a valid species and hence that the name T erythrocephalus 

 applies exclusively to the European representative. Many of the geographi- 

 cally intermediate southwestern variants of T. posticus display anatomical 

 conditions that are intermediate between those of its eastern population 

 and T. californiensis, showing that these taxa were once united in a 

 single species spanning the breadth of North America through the 

 southern United States and the adjacent part of Mexico (Shelley 1990a). 

 This knowledge indicates that the phenotypic resemblance between T. 

 californiensis and T. erythrocephalus represents convergence, but it 

 is an especially perfect example with no clear differences in their 

 external anatomies. At present, I can only use geography to distinguish 

 them in the key and assign specific names, and the search for differences 

 requires substantially more critical information as might derive from 

 comparative biochemistry. Theatops californiensis and T. erythrocephalus 

 are thus prime candidates for investigation by immunological techniques 

 and .electrophoresis of haemolymph proteins. 



Still another fascinating aspect of Theatops is the adaptability 

 of T. phanus Chamberlin, which is known only from caves in Sutton 

 and Menard counties, Texas, where it displays troglobitic adaptations. 

 These include pallid color and long, slender appendages, the antennae 

 reaching back to tergites 6-7, instead of to tergites 3-4, the antennomeres 

 being three to five times longer than wide, instead of about twice 

 as long, and the podomeres on the penultimate legs being four to 

 five times longer than wide, as opposed to only two to three times 

 longer (Weaver 1982). Some cave specimens are quite large, and the 



