EUPLECTINI 119 



Key to Melba s.s. Males 



The following unsatisfactoiy key is based on the male sex only. The females 

 have only six sternites, whereas the males have seven sternites, the seventh 

 being in the form of a small oval subcircular, or more rarely subrhomboidal 

 plate. This plate (operculum, pygidium) is uncarinated medianly, asym- 

 metrically articulated, and enclosed by the incised sixth stemite and fifth 

 tergite. It should be noted that one species {longicollis Raffray) is a guest of 

 ants. 



Third, fourth, and fifth sternites presumably simple, without tubercles, 

 foveae or conspicuous depressions (Raffray in describing these two 

 species discusses the male characters but makes no mention of such 



sternal modifications ; types not seen) 2 



Third, fourth, and fifth sternites with at least one segment secondarily 

 modified, often two segments modified by foveae, tubercles or de- 

 pressions 3 



2. Metasternum longitudinally sulcate; sternites II to V subequal in 



length; stemite VI medianly flattened; 0.9-1.0 mm. in length 



crassipes 



Metasternum flattened; sternites II to V progressively shorter; stemite 

 VI transversely impressed; 0.9-1.0 mm. in length grenadensis 



3. Third sternite with a median transverse impression; fifth sternite with 



two approximate transverse foveae; 0.6-0.7 mm. in length 



inconspicua 



Third sternite otherwise modified 4 



4. Third sternite with a tubercle on each side; 0.75 mm. in length 



specularis 



Third sternite otherwise modified 5 



5. Third sternite with an impression on each side, this depression sub- 



tuberculate; metastemum not strongly impressed; 1.0 mm. in length 



gibbula 



Third sternite with an oblong, arcuate foveoid depression on each side ; 

 metasternum longitudinally impressed; length 1.0 mm eggersi 



This key does not take into account a remarkable myrmecocolous species, 

 Melba longicollis Raffray from a nest of Atta lundi in Argentina. This species 

 is 1.10 mm. long and the male has the anterior and the intermediate femora in- 

 flated and the intermediate tibiae dentate. It is said to be near dentipes Raffray 

 of Pennsylvania but to have a more elongate-oval pronotal outline. 



It is possible that both Sharj^'s species, which are placed in Frontelba, 

 belong in Melba s.s. 



The species of the genus Melba may be listed as follows: 



Melba s.s. 



Tenth antennal segment not bilaterally asymmetrical ; vertex of head with 

 the vertexal foveae connected by an arcuate, more or less defined sulcus ; vertex 



