Springtails (Collembola) of the St. Louis Area 9 
the following segments beginning at the proximal end: two pre- 
coxa, coxa, trochanter, femur, tibio-tarsus. At the end of the 
tibio-tarsus there is either one claw, the unguis, or an unguis 
and a smaller claw, the unguiculus. This order is subdivided 
into two suborders: 
Body elongate with the segments distinct, last two or three 
abdominal segments are often more or less fused in some species. 
Suborder Arthropleona Borner. 
Body subglobose with thoracic and abdominal segments fused 
except for ‘the last two segments of the abdomen. Suborder 
Symphypleona Borner. 
Families of the Suborder Arthropleona Borner, 1901: 
Prothorax naked dorsally and usually covered by a forward 
Projecting mesonotum, furcula usually present; absent only in 
the genus Anurophurus. Entomobryidae Tomésvary. 
Prothorax with dorsal bristles and not covered dorsally with 
forward projecting mesonotum. Poduridae Lubbock. 
Subfamilies of the Family Entomobryidae Tomosvary, 1883: 
Tergum of the fourth abdominal segment much longer than 
the third. Subfamily Entomobryinae Schiffer. 
Tergum of the third and fourth segments subequal, body 
scaled, third and fourth segments of antennae subsegmented. 
Subfamily Tomocerinae Schaffer. 
Body not scaled, third and fourth segments of abdomen sub- 
equal, third and fourth segments of antennae rarely annulate. 
Subfamily Jsotominae Schiffer. 
Famlies of the Suborder Symphypleona Borner, 1901: 
