The Ants of the Baltic Amber. 



103 



but owing to his inability to attach it to any of them, he described 

 it as distinct. It has 12-jointed antennae and measures only 3 mm. 



Genus JRhopalomyi^'mex Mayr. 



Rhopalomyrmex pygmoeus Mayr. (Fig. 49.) 

 Rhopalomyrmex -pygmoeus Mayr, Beitr. Naturk. Preuss. I, 1868, p. 42, Taf. II, 

 Fig. 25, 26, 2; Dalla Torre, Catalog. Hymen. VII, 1893, p. 175: 

 Ern. Andre, Bull. Soc. Zool. France, XX, 1895, p. 82; Handlirsch. 

 Foss. Insekt. 1908 p. 859. 



The genus Rhopalomyrmex was founded on this single species, 

 which in turn was based on a single specimen (7576/290) in tho 

 Geolog. Inst. Koenigsberg Coll. This has since been mounted in 

 a balsam cell and is in such a \/ 



position that all its parts, except 

 the anterior portion of the head, 

 can be easily seen. I have found 

 12 specimens of this species, one 

 in the Klebs Coll. (K 789) and 

 11 in the Geolog. Inst. Koenigs- 

 berg Coll. 10 workers (B 19096, 

 B 19821, XXB 745 and 7 without 

 numbers) and a single male 

 (XXB 175). These are all beau- 

 tifully preserved. 



As Mayr observed, Rhopa- 

 lomyrmex pygmceiis closely re- 

 sembles Plagiolepis kunowi and 

 the living P. pygmcea Latr. but 

 has 10-jointed antennae and the p. 

 four terminal joints forming a club, 

 which, however, is not very 



sharply marked off from the remainder of the funiculus. These 

 are really the only characters which separate the genus Rhopa- 

 lomyrmex from Plagiolepis. From the neotropical genus Myrmclachista 

 Roger, the workers of which also have 10-jointed antenna-, the amber 

 genus is distinguished only by having a 4- instead of a 3-jointed 

 antennal club. It is therefore doubtful whether Rhopalomyrmex is to 

 l)e regarded as more than a subgenus of Plagiolepis or Myrmelachisia. 



What I take to be the male of Rh. pygmtcus measures only 3 mm. 

 The body is slender, both the thorax and gaster being long and narrow. 

 The head is broader than the thorax, with moderately large eyes and 



49. Rhopalomyrmex pygmaeus Mayr. 

 Worker, K 7S9. 



