586 ^ CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



echidna flea from Australia, and a giant flea from northern Canada. By 1853, 

 only two genera, Pulex and Ceratophyllus, were recognized and no general clas- 

 sifications had been attempted. 



The first systematic account of the order was that of Kolenati (1863), who 

 recognized eight genera. The more conservative Taschenberg recognized but 

 five in his important work (1880), which was the standard reference on fleas 

 at the end of the nineteenth century, when three outstanding students of the 

 order made their appearance in the literature. These were Julius Wagner of 

 Russia, N. Charles Rothschild of England, and Carl F. Baker of the United 

 States. These men had a purely academic interest in the fleas, for in those days 

 the role of these insects as vectors of plague and other diseases was not known. 

 The effect of the attack by this trio, and by some lesser students, on the virtually 

 untouched fauna during the next few years is well demonstrated by three world 

 lists published by Baker over a ten-year period. In 1895 he listed but 35 species 

 (actually, he missed a few), which he placed in three families and six genera. 

 In 1904 he catalogued 134 species, and in 1905, as a result of "a most extraordi- 

 nary activity among students of this group," supplemented this list by approxi- 

 mately 120 additional names, arranging the whole into eight families. 



About this time, the association between fleas and the dreaded l)u1)onic plague 

 was proved in India. There followed immediately a tremendous increase of in- 

 terest in these insects, and the few specialists available found their services much 

 in demand. Baker ceased work on fleas in 1905, but Rothschild and Wagner con- 

 tinued to occupy leading positions. The former purchased specimens from col- 

 lectors all over the world, and, in 1915, established a publication {Ectoparasites) 

 that was devoted almost exclusively to papers on the taxonomy of fleas. Dampf 

 of Germany published a number of papers that were particularly well illus- 

 trated for their time. Oudemans, the great Dutch acarologist, published papers 

 on flea phylogeny, in one of which (1909) was proposed a subordinal division 

 that was followed for many years and has been discarded only recently. The 

 most outstanding student of fleas, the former friend and colleague of Charles 

 Rothschild, is Karl Jordan, whose work on the order extends over half a century. 

 First assisting Rothschild (illustrating many of the early Rothschild papers), 

 then publishing jointly until the latter's death in 1923, and since then continu- 

 ing alone, Jordan has described more species and exerted more influence on the 

 development of a natural classification of these insects than any other individual. 

 His nearest competitor was Julius AVagner, who left Russia after the revolution 

 of 1917 to live in Yugoslavia. Shortly before his death, Wagner sold his collec- 

 tion to the Staatsmuseum in Hamburg and it is known that the larger portion 

 of it perished when the museum was destroyed by bombing during World War 

 II. Wagner described many genera and species and published a number of works 

 on flea morphology as well as a catalogue of the Palearctic species and several 

 papers on classification, of which the most important appeared in 1939. The 

 framework of our knowledge of the fleas of the world is based largely on the 

 works of Rothschild, Jordan, and Wagner. 



The first half of the twentieth century has been a period of species descrip- 

 tion and discovery of new specific distinctions. In 1900, for instance, Rothschild 

 drew, for the first time, attention to the taxonomic value of the terminal ab- 

 dominal segments of the female, and to specific differences in the spermatheca. 



