CONTENTS 



Page 



lutroduction 'l 1 



Notes on the evolution of the mucrones 3 



Phylogenetic and taxonomic notes 4 



Definitions 7 



Family Isotomidae 7 



Key to genera of Isotomidae 8 



Genus Tetracanthella 10 



Genus Anurophorus 12 



Genus Folsomides 13 



Key to species of Folsomides 14 



Genus Isotomodes 16 



Genus Folsomia 19 



Key to species of Folsomia 19 



Genus Guthriella 33 



Key to species of Guthriella 33 



Genus Proisotoma 38 



Key to subgenera of Proisotoma 38 



Subgenus Ballistura 39 



Key to species of Ballistura 39 



Subgenus Proisotoma 43 



Key to species of Proisotoma 43 



Genus Archisotoma 66 



Genus Agrenia 68 



Genus Isotomurus 70 



Genus Isotoma 78 



Key to subgenera of Isotoma 78 



Subgenus Pseudisotoma 78 



Subgenus Vertagopus 81 



Key to species of Vertagopus 81 



Subgenus Isotoma 87 



Key to species of Isotoma 87 



Unidentified species 116 



Literature cited 120 



Explanation of plates 129 



Index 141 



III 



