MONOGRAPH OF THE NORTH AMERICAN PROCTOTRYPID.E. 107 

 Tribe ii. — B.eini. 



This tribe is of small extent, apparently, and for the most part, com- 

 prises siiecies of the smallest size, the majority of which rarely attain 

 one millimeter in length. 



The habitns of the species more closely resembles the Telenomini, but 

 the solid antennal club of the female, the diflerence in venation of the 

 winged forms, the marginal vein being puuctiform, or short and stout, 

 the .stigmal vein short, thickened at base and terminating in a small 

 rounded stigma, while the basal nervure is usually present, and the 

 third abdominal segment, not the second, being- the largest, readily 

 distinguish them. These dift'erences and the position of the lateral 

 ocelli will also separate them at once from the other tribes. 



The tribe Ba'ini, as at present defined, will contain five genera: Thoron 

 Hal., Aeolus Forst., Acoloides How., Ceratobwm Ashm., and Bcvus Hal., 

 the parasitism of three of which is known. 



Species in the genera Acola.s, Acolohles, and Bams have been reared 

 in America from spider eggs ; and I should not be in the least surprised 

 to learn, from future observations, that the whole group confine their 

 attacks to Arachnid eggs. 



The genera may be distingtushe<l by the aid of the following table: 



TABLE OF GENERA. 



FEMALKS. 



Apterous forms 2 



Wiuged. 

 First abdominal segment without a horn at base. 

 Mesonotnm with 2 furrows; lirst abdominal segment petiolifonn; eyes bare; 



lateral ocelli distant from the margin of the eye Tiiokon Hal. 



First abdominal segment with a horn at base. 



Mesonotnm without furrows Ceratob.eus Ashm., gen. nov. 



2. Scutellnm distinct. 



Mesonotnm without furrows; lateral ocelli close to the eye. 



First abdominal segment with a horn at base Ceratob.eL's. 



First abdominal segment without a horn at base. 



First abdominal segment as broad as the metathorax and only visible as a 

 transverse line; face with an antennal impression, the occiput con- 

 cave, the superior margin sharp Acolus Fiirst. 



First abdominal segment snbpetiolate, much narrower than the metathorax ; 

 face not or but slightly imi)re.ssed, the superior margin of the occi- 

 put rounded Acoloides How. 



Scutellnm wanting B^eus Hal. 



Winged, 



Mesonotnm with two furrows ; lateral ocelli distant from the margin of the eye. 

 Antenna; filiform, the flagellar joints about three times as long as thick. 



Tiiokon Haliday. 



