276 Journal New York Entomological Society. [Vol. xxiv. 



3. With but one (the median) terminal caudal filament. 



Dasyleptoides (Mononemura). 

 With three caudal filaments 4 



4. Head in frontal view deeper than broad. Styliform appendage usually 



found on coxa of meso- and metathorax. Tarsi usually three-segmented. 



Machioides (Trinemura). 

 Head in frontal view broader than deep. No styliform appendage on coxa 

 of meso- and 'metathorax. Tarsi usually two-segmented. 



Lepismatoides (Thysanura). 



5. Styli present on first abdominal sternum. Abdomen with terminal forceps, 



or with segmented cerci 6 



Styli wanting on first abdominal sternum. Abdomen with segmented cerci, 

 whose terminal segment is imperforate .... Campodeoides (Rhabdura). 



6. Abdomen with segmented cerci whose terminal segment is provided with an 



apical aperture Projapygoides (Prodicellura). 



Abdomen with forceps Japygoides (Dicellura). 



7. Vestigeal legs of first abdominal segment united and modified to form a 



ventral tube (in some cases reduced to a mere vestige). Antennae usually 

 present. Abdominal segments usually not exceeding six in number.... 8 

 Vestigeal legs of first abdominal segment not united to form a ventral tube. 

 Antennae usually absent. Abdominal segments usually nine to twelve in 

 number Eosentomoides (Protura). 



8. Abdomen sub-cylindrical : segments usually distinct. 



Entomobryoides (Euarthrura). 

 Abdomen sub-globular : segments wholly or in part grown together. 



Smithuroides (Synarthrura). 



There is some doubt as to whether the fossil Dasyleptidse con- 

 stitute a distinct order, or are merely to be regarded as a suborder 

 of the forms with three caudal filaments. The Projapygidae also 

 might better be regarded as a suborder of the Dicellura (Japygidse), 

 than as a distinct order. Brues and Melander group them with the 

 Rhabdura (Campodeidse) in an order in which the Japyigidae are not 

 included; but if the Projapygidae are not to be considered as forming 

 a distinct order, they should be grouped with the Dicellura (Japy- 

 gidae), since their afifinities are with the Dicellura, rather than with 

 the Rhabdura (Campodeidae). Handlirsch and his followers regard 

 the Entomobryidae and Sminthuridae as representing distinct orders, 

 while Boerner (who gave them the names Arthropleona and Symphy- 

 pleona) regards them as representing suborders rather than as dis- 

 tinct orders. 



It is possible that such insects as Troglopedetes (family Troglo- 



