110 
William Morton Wheeler 
Of this, the type species of the genus Gesomyrmex, Mayr men- 
tions 19 workers, 6 of which (168/21, 273/36, 320/41, 7631/345, 
7666/380 and 9361/539) belonging to the Geolog. Inst. Koenigsberg 
Coli., I have examined. One of these (7666/380), as previously stated, 
is a specimen of G. annectens. Besides these I have examined 112 
workers of G. hoernesi , which are distributed as follows: 88 in the 
Geolog. Inst. Koenigsberg Coli. (B 14123, B 19762, B 27253, XXB 
701, B 18982, B 5110, B 18859, XXB 1213, B 19313, B 18390, 
XXB 7048, XB 224, B 18690, XXB 64, XXB 899, B 18502, XXB 
800, B 18190, B 19806 etc.), 20 in the Klebs Coli. (K 4478, K 836, 
«119, K 4466, «111, K 2614, K 939, K 889, «124, «95 etc.), one 
in the Brussels Museum, one (265) in the Berlin Museum and 2 in 
the Haren Coli. (1498, 2646). 
Mayr described what he took to be the male of this species 
from a single very poorly preserved specimen in opaque, brown amber 
(258/33 in the Geolog. Inst. Koenigsberg Coli.). After examining this 
specimen, which has probably deteriorated with time, I have nothing 
to add to the description. It still shows the shape of the mandibles, 
the enormous eyes, the short, 11-jointed antennse, the long, linear 
external genitalia and the venation of the wings, with their discal, 
single cubital and closed radial cells. With the discovery of an ad- 
ditional species of Gesomyrmex , however, this male *s not so clearly 
referable to G. hoernesi as it was in Mayr’s day, and it is not im- 
possible that it may even be the male of one of the two species of 
Dimorphomyrmex that have since come to light. Unfortunately this 
question cannot be settled tili we obtain the hitherto unknown males 
of the recent' species of Gesomyrmex and Dimorphomyrmex. 
An interesting consideration is suggested by the four amber 
species of these two genera described above. It will be seen that 
they form a graded series in the Order of their description. While 
the coloration, pilosity and, in its essential features, also the sculpture 
are the same in all four, the body d windles in size, the eyes gra- 
dually increase in size and the clypeal lobe, palpi, mandibles and 
funicular joints increase in length as we pass from D. theryi through 
D. mayri and G. annectens to G. hoernesi. At first sight we might 
be tempted to regard all four of these forms as the workers of a 
single polymorphic species, but this is evidently not the case as shown 
by the worker minor of D. theryi. We may assume, therefore, that 
they represent four different stages in the early Tertiary evolution 
of two genera, D. theryi being the oldest and most primitive and 
G. hoernesi the most recent and dominant type. The existing species 
