36 nULLETIN 45, UNITED .STATES NATIONAL MUSEUM. 



In stating this genus to be synonymous with ]\resltii(s Spinola and 

 Heterococlia ])ahll)()ni, Prof. Westwood erred and added not a little to 

 the confusion resi)ectiug it, as all these genera are quite distinct. Hc- 

 teroccelia is, as Dahlbom iudicated, a genus in the family Chrysididcv, 

 while 3[esitius is a genus allied to Upyris. For an explanation of this 

 statement see my remarks under the genus Mesitius. 



The genus is found associated with various ants; it may be parasitic 

 upon the ants, or upf»n the myrmecophilous Coleox^tera so frequently 

 found in their nests. 



Our species may be recognized by the aid of the following table: 



TABLE OF SPECIES. 

 MALES. 



Mesonotum without furrows 3 



Mesouotuin with furrows. 



Transvcr.se median nervuro interstitial 2 



Transverse median nervure evected. 



Antenn;p and legs pale ferruginous I. magxim sp. uov. 



2. Wings subliyaline. 



Abdomen piceous, paler at sutures, rufescent l)eneath. 

 AntenuiB and legs pale ferruginous or lirowni.sli yellow. 



Mandibles with small teeth within I. MYRMECorHiLUM, sp. nov. 



Mandibles very large aud broad without teeth within. 



I. MAXDIBULARE, Ashm. 



Wings hyaline. 



Abdomen rufous, sometimes more or less piceous toward base above. 

 Antennie and legs pale ferruginous. 



Abdomen not longer than the thorax I. rlfivkxtre, sp. nov. 



Abdomen brownish-yellow. ' 



Abdomen elongate, luueh longer than head and thorax together. 



I. MONTAXUM sp. nov. 



3. Wings subhyaliue. 



Black; legs pale ferruginous, the femora olifuscated above. 



I. FLORIDAXUM Asluu. 

 P^EMALES. 



Head l)lack, with large ])unctures. 



Thorax dark brown, or mahogany. 



Abdomen not longer than the tliDrax. ruCo-piceous I. myrmecophilum 



Thorax rufous. 

 Abdomen brownish-yellow, much longer than the head and thorax united. 



I. MOXTANUM 

 Head piccons. 



Thorax rufo}dceous. 



Abdomen brownish-yellow, longer than tlie head and thorax together. 



I. MANDIBTLARE 



Isobrachiuni magnnni sp. nov. 



S . — Length nearly 5""", Black, ])unctate; liead a little longer than 

 wide, rather strongly punctate, the surface alutaceous. Antenna' 13- 

 jointed, brownish-yellow, the liagellar joints from 1} to 2h times as long 



