Myrmicinae

1a. Tiny ant, antennae with 10 segments; no propodeal spines; tiny eyes (< 15 ommatidia)  Solenopsis 
1b. Antennae with 11 or 12 segments  2
  
2a.  Antennae with 11 segments  3 
2b. Antennae with 12 segments  6 
 
3a. Gaster heart-shaped; petiole attached dorsally to gaster   Crematogaster 
3b. Gaster not heart-shaped; petiole attachment anterior  4
  
4a. Frontal carina short, no antennal scrobe (groove in which antenna sits)   5 
4b. Frontal carina longer (extending beyond eye), forming an antennal scrobe   Protomognathus americanus  
  
5a. Eyes with short, erect hairs between the ommatidia  Fromicoxenus provancheri 
5b. Eyes without erect hairs between the ommatidia Leptothorax (muscorum group) 
  
6a. Petiole short, no scale or node, and with no anterior peduncle. Two pairs of propodeal spines   Myrmecina  americana  
6b. Petiole usually with a node and distinct anterior peduncle. 0 or 1 pair of propodeal spines    7
  
7a. Posterolateral portions of clypeus raised into a sharp ridge (“carina”) that forms an antennal socket.Sting  with small triangular appendage on dorsal end. On rocks and pavement. Tetramorium caespitum   
7b. Sting simple, clypeus “normal” 8
  
8a. Middle and hind tibial spurs finely pectinate (view at 100x); thorax with modest break between segments,  furrows/rugae on sides  Myrmica 
8b. Middle and hind tibial spurs simple or absent. Maxillary palps #5-segments; labial palps # 3 segments  9
  
9a. No spines on propodeum; antennal club with 3 segments  Monomorium 
9b. Spines on propodeum   10
 
10a. Antennal club 3-segmented  11
10b. Antennal club 4-segmented  12
  
11a. Workers dimorphic (large, small); majors (large workers) with huge heads normally with distinct occipital  lobes. “Sutures” impressed on rear side of altitrunk  Pheidole 
11b. Workers not dimorphic, head proportions normal  Temnothorax 
 
12a. Antennal scapes short , not reaching occiptal border; eyes small or vestigal; small ants (2.5-4.3mm long)  Stenamma 
 12b. Eyes prominent, antennal scapes longer; antennal club prominent, larger ants; clypeus lacking a ridge;  thorax with large break between segments  Aphaenogaster 

Tetramorium caespitum