THE TRIBE CHALCIDINI — BURKS 265 



4. Metanotum and propodeum uniformly and densely covered with 



long setae; abdomen strongly compressed nigricornis group (p. 278) 



Metanotum sparsely setose, propodeum usually with only a few 

 setae at lateral margins, disk of propodeum always entirely 

 without setae; abdomen not compressed femorata group (p. 291) 



These groupings of species have been made solely for convenience 

 in their treatment. The groups are not sufficiently distinct to be 

 considered as separate genera, for when specimens from the Neo- 

 tropical area are studied intergrades are to be found between these 

 groups. 



The transitiva Group 



All the members of the transitiva group have distinct lateral 

 carinae on the frons parallel to the anterior margins of the compound 

 eyes; the scrobe cavity is deep and the margins are distinctly cari- 

 nate; the malar space is quite narrow, one-third or less the height 

 of the compound eye ; the metaf emora have, with one exception, only 

 four teeth; one species has (see fig. 12, e) acquired one or two addi- 

 tional small teeth near the base, and the large apical tooth is rather 

 indistinctly subdivided. 



The transitiva group includes those members of the genus that may 

 be considered the most primitive. The genus Spilochalcis is un- 

 doubtedly derived from some ancestral form having slender meta- 

 femora. A few large teeth were probably developed first on the 

 ventral margin, and later these large teeth were replaced by a num- 

 ber of smaller ones; at the same time, the femora gradually became 

 much thickened. One species of this group, S. exomata (Cresson), 

 has rather slender metaf emora and four large teeth (fig. 12, a). In 

 other species the gradual increase in width of the metafemur can be 

 seen (fig. 12, h-d)^ and in S. phoenica described below and the extra- 

 limital species /S. compactilis (Cresson), the transition to a form with 

 many small teeth can be seen. In these two species the addition of 

 small teeth at the base and the beginning of the subdividing of the 

 large apical tooth have occurred (fig. 12, e). 



KEY TO SPECIES OF THE TRANSITIVA GROUP 



1. Outer basal tooth of metafemur larger and longer than others 



(fig. 12, 6) eubule (p. 269) 



Outer basal tooth of metafemur not larger than others 2 



2. Metafemur elongate, narrow (fig. 12, a) exornata (p. 266) 



Metafemur semiglobose (fig. 12, c-e) 3 



3. Outer ventral margin of metafemur with only four teeth 4 



Outer ventral margin of metafemur with six or seven teeth, api- 

 cal ones obscure (fig. 12, e) phoenica (p. 276) 



4. Outer basal tooth of metafemur small (fig. 12, c) dorsata (p. 272) 



Outer basal tooth of metafemur large (fig. 12, d) transitiva (p. 274) 



