INTEODUCTION. 6 



mation witli reference to extra European species is as 

 yet very meagre. 



The synonymy of tlie group is unfortunately much 

 involved. This has arisen partly from the fact that the 

 descriptions given by the earlier writers, excepting 

 always De Geer, are so short that it is in many cases 

 impossible to determine satisfactorily the species, or 

 even the genus ; partly from the fact that some species 

 vary very much in colour, and partly from the accident 

 that Bourlet and Nicolet, who have described a consi- 

 derable num.ber of species, published the results of their 

 labours almost simultaneously, and without being aware 

 of one another's writings. Under these circumstances 

 I have thought it desirable to give lists of the names 

 used by some of the principal writers on the group, 

 together with those by which I think the species should 

 be known. In some cases, however, the species are 

 unfortunately quite undeterminable from the characters 

 given, and others, probably, are mere varieties of one 

 another. 



The first memoir on the group to which I think it 

 necessary to refer was published by De Geer^ under 

 the title " Experimenta et Observationes de parvulis 

 insectis, agili saltu corpuscula sua in altum levantibus, 

 quibus PodurcB nomen est, exhibitse." He describes in 

 detail, and with his usual accuracy, four species, viz. 

 Podura campestris nigra, our Isotoma arhorea ; Podura 

 camijestris cinerea == Degeeria nigromaculata ; Podura 

 aquatica nigra, still known as P. aquatica ; and Podura 

 aquatica cinerea, which is our Isotoma stagnormn. The 

 memoir is illustrated by four plates. 



Three years later De Geer published a second memoir,^ 

 in which he described and figured the first species of 

 Smynthurus, 8. fuscus. He recognised its affinities to 

 the Poduridce, and described it as follows : — " Podura 

 fusca, globosa, nitida, antennis longis, articulis pluri- 

 mis." 



1 ' Acta Soc. Reg. Sci. Upsaliensis,' 1740, p. 48. 



' ' Koiigl. Swenska Wet. Acad. Hand.,' 1743, p. 296. 



