230 HYMENOPTERA OF AMERICA. [PART I. 



2,2. The first abdominal segment margined with yellow. 



3. All the segments margined with yellow 



4. Prothorax all yellow. 72. Guadulpensis. 



4, 4. Prothorax margined with yellow. 



72. / Guadulpensis. 



5. The posterior margin of prothorax yellow. 73.-; zonatus. 



76 <■ La Plulie. 



5, 5. Only the anterior margin of prothorax yellow. 



6. Thorax wholly or nearly black ; abd. much truncate at 

 base. 70. Peruen&is. 



6, 6. Thorax slightly ornamented with yellow ; abdomen more 



ovate. 71. brachygaster, 



3, 3. Only the first two-segments margined with yellow or luteous. 



4. The following segments rnfous. 78. cubensis. 

 4,4. The following segments black. 



5. The posterior margin of prothorax, or both margins, yellow. 



6. Ornaments whitish. * < '"■'/'• 



79. t rali/ornicus. 



6, b. Ornaments yellow. < ' 



7 b". I La Platce. 



5, 5. Only the anterior margin of prothorax yellow. 



6. Ornaments whitish. 



7. Insect short, thorax cubical. 74. Gayi. 



7, 7. Insect more slender, thorax longer than wide. 



79. californicus. 

 6,6. Ornaments yellow, insect not so stout. 77. tibialis. 

 1, 1. Body more or less adorned with rufous. 



2. Prothorax and first abdominal segment, etc., rufous. 



81. Erinnys. 

 2, 2. Only the extremity of the abdomen rufous. 78. cubensis. 



Description of the species. 



1st. Section. — Tliorax cubical (at least among the males) or 

 square, more lengthened. Abdomen conical; the first seg- 

 ment very large, as wide as the second. 



In this group one finds the most thick-set forms in the whole 

 tribe of solitary wasps (<>. nasidens, 0. Gayi), the thorax 

 becoming perfectly cubical, as in the Nectarinia, among the social 

 wasps. However, among the most part of the species the forms 

 do not differ essentially from those of the insects of the division 

 Odynerus. 



