14 
Psyche 
[Vol. 92 
N. agi/is. Propodeum more flattened in side view, the basal and 
posterior faces merging as a single smoothly convex curve; pilosity 
denser. 
N. californicus. Petiolar node more flattened in side view; body 
pilosity denser. 
N. emersoni. Basal and posterior faces of propodeum meeting 
at only slightly more than right angle; pilosity denser. 
N. fallax. Antennal scapes thicker and shorter relative to head 
capsule; subpetiolar process slightly thicker and pointing straight 
down (instead of forward as in ectopus). 
N. manni. Occipital border flat; pilosity denser. 
N. melanocephalus. Occipital border distinctly less concave; 
pilosity denser. 
Of these 6 species, no fewer than 5 have ranges predominantly in 
Mexico and the southern United States, the northern portion of the 
range of Neivamyrmex. Only one ( emersoni ) is limited to the south- 
ern part of the total generic range, in this case South America and 
Trinidad. Yet only 21 of the 61 Neivamyrmex species occur in the 
northern portion; the remaining are so far as known limited to 
South and Central America. Put another way, ectopus closely 
approaches about 20% of the known northern species but only 
about 2.5% of the southern species. 
Discussion 
The exact age of the Dominican amber is unknown, but most 
writers agree that it is either late Oligocene or early Miocene. The 
material originates from various mines in two principal areas: in the 
north of the Dominican Republic between Santiago and Puerto 
Plata, and in the east between Santo Domingo and the Bahia de 
Samana. The age of the many deposits in which insects occur no 
doubt varies. Foraminiferal fossils associated with amber from 
mines near Palo Alto are characteristic of the lower Miocene 
(Baroni-Urbani and Saunders, 1982). I would guess a relative youth 
for most of the ant fossils I have seen, because the great majority 
belong to modern genera. 
Regardless of its exact age, the discovery of a Neivamyrmex in 
Dominican amber has considerable significance for the interpreta- 
