24 
Psyche 
[Vol. 92 
The problem is further complicated by the separation of workers, 
queens, and males into different amber pieces, so that most linkages 
across castes and sexes can only be guessed. In the case of the 
Dominican amber, however, I was able to solve the problem in part 
by the discovery of three miniature “Rosetta stones”: 3 amber pieces 
with closely intermingled workers and males of the commonest spe- 
cies of Azteca (A. alpha). One of the pieces also contains a male 
pupa, further supporting the interpretation that the associated 
workers and males belonged to the same colony and were trapped 
during a colony emigration. 
With the worker-male connection secured, I made comparisons 
with material representing 48 contemporary species of Azteca and 
50 of Iridomyrmex (11 Neotropical, 39 Indo-Australian) in the 
Museum of Comparative Zoology collection, many with workers 
and males from the same nests. The following characters appear to 
hold with consistency: 
1 . In Azteca workers the mesonotum is usually moderately con- 
vex in side view and hence does not form a smooth line with the 
pronotum; in New World Iridomyrtnex workers the mesonotum is 
only weakly convex in side view and forms a continuous line with 
the pronotum. 
2. In Azteca workers the dorsal face of the propodeum is much 
less convex in side view than in Iridomyrmex workers. 
3. In Azteca workers the petiolar node is longer than high (the 
reverse is true in Iridomyrmex) and inclined more strongly forward 
than in Iridomyrmex. 
4. The occiput of Azteca workers is usually more deeply con- 
cave than in Iridomyrmex workers, although extreme species within 
the two genera overlap. 
5. In Azteca males, the scape is very short, no longer than the 
combined second and third antennal segments, while either the 
second or third segment (depending on the species) is notably elon- 
gated, inflated, or both. In Iridomyrmex males, the antennae are 
more typical, with relatively long scapes and unmodified funiculi; an 
exception is I. iniquus, which has the Azteca antennal form. 
6. In Azteca males the mandibles are short and triangular, lack- 
ing a well-defined masticatory border; whereas in Iridomyrmex 
males the mandibles have a well-defined masticatory border which 
also often bears serially arranged teeth. 
