206 AMERICAN HYMKNOPTERA. 



Tribe EXOCHINI. 



1. Abdomen petiolate. sometimes broadly so ; spiracles of first segment placed in 



or behind the middle 2. 



Abdomen sessile, or nearly so ; spiracles of first segment placed in or before 

 the middle 5. 



2. Hind tibia? with a single small spur Periope Curtis. 



Hind tibiae with two spurs 3. 



3. A reolet wanting; second member in % antennae excavated. 



Alcocerns Foer. 

 Areolet present 4. 



4. Metauotura smooth and glabrous Exochoides Cress. 



Metanotum areolated ; face slightly convex •■■ Ischyrocneillis Holmg. 



5. Metanotum not areolated at base ; petiole long and clavate. 



* Colpotrochia Holmg. 

 Metanotum usually areolated at base ; petiole broad and short 6. 



6. Second abdominal segment with median carina Chorinseus Holmg. 



Second abdominal segment without median carina 7. 



7. First member of flagellum decidedly longer than the second 8. 



First member of flagellum not or scarcely longer than the second, and the 



following segments very short. 12. 



8. Pleural areas of metathorax not separated by a transvei'se carina 9. 



Pleural areas of metathorax usually separated by a sharp ti-ansverse carina. 10. 



9. Areolet present Triclistus Foer. 



Areolet wanting f Amesoly tliS Foer. 



10. Vertex separated from occiput by a sharp ridge Metaceelus Foer. 



Vertex and occiput without sharp ridge between them 11. 



11. Metanotum with three median caringe * Polyclistus Foer. 



Metanotum with two median carinfe E.xocliiis Grav. 



12. Vertex separated from the occiput by a sharp ridge ; abdomen broad, clavate. 



Hyperacmus Holmg. 

 Vertex oval, without sharj) ridge : abdomen long, truncate at apex. 



mima Davis. 



PERIOPE Curtis. 

 (Guid. ed. i, App., 538a.) 

 Monoplectron Holmgren, Monog. Tryph. Suec. 305, 1856. 

 Oligoplectron Foerster, Synop. Fam. und Gatt. Ich., 1868. 

 Periope iethiops Cress. yTryphon), Trans. Amer. Ent. Soc. ii, 106. 



"^ . — 7 mm. Black, with the tegulte, large stripe beneath, front legs beyond 

 middle of femora, basal half of four posterior tibiae, apex of middle femora and 

 most of venter yellow ; four posterior tarsi yellowish brown ; antennae brown, 

 dark fulvous on apical half; wings subhyaline, nervures and stigma brown; 

 areolet present, triangular ; stigma thick, rounded on each side, making it elon- 

 gately elliptical; second recurrent nervure sinuate; head flat, much elongate 

 beneath ; face oval, pilose ; clypeus large, not separated : ligula long, as in Apidae, 

 palpi slender; antennae large, strongly clavate and with short segments; thorax 

 broader than head, subrotund, pilose ; mesothorax closely punctured ; parapsidal 

 grooves present anteriorly; metathorax oval, obliquely truncate, areolated. apical 

 areas large, basal transverse carina wanting, metapleura polished, sparsely punc- 

 tured ; abdomen compact, oval above, subclavate, punctured and pilose ; basal 



