The Ants of the Baltic Amber. 
103 
(7576/290) in the 
been mounted in 
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 Rhopalomyrmex Mayr. 
Rhopalomyrmex pygmoeus Mayr. (Fig. 49.) 
Hhopalomyrmex pygmceus Mayr, Beitr. Naturk. Preuss. I, 1868, p. 42, Taf. II, 
Fig. 25, 26, Dalla Torre, Catalog. Hymen. VII, 1898, p. 175: 
Ern. Andre, Bull. Soc. Zool. France, XX, 1895, p. 82; Handlirscb, 
Foss. Insekt. 1908 p. 859. 
The genus Rhopalomyrmex was founded on this single species, 
which in turn was based on a single specimen 
Geolog. Inst. Koenigsberg Coli. This has since 
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 Coli. (K 789) and 
11 in the Geolog. Inst. Koenigs- 
berg Coli. 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 pygmceus closely re- 
sembles Plagiolepis künowi and 
the living P. pygmcea Latr. but 
has 10-jointed antennse and the 
four terminal joints forming a club, 
which, however, is not very 
sharply rnarked 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 Myrmelachista 
Roger, the workers of which also have 10-jointed antennse, 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 
be regarded as more than a subgenus of Plagiolepis or Myrmelachista. 
What I take to be the male of Rh. pygmceus 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 
Fig. 49. 
j Rhopalomyrmex pygmaeus Mayr. 
Worker, K 789. 
