WQ 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 

 Coll., 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 Coll. (B 14123, B 19762, B 27253, XXB 

 701, B 18982, B5110, 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 Coll. (K 4478, K 836, 

 a 119, K 4466, a 111, K 2614, K 939, K 889, a 124, a 95 etc.), one 

 in the Brussels Museum, one (265) in the Berlin Museum and 2 in 

 the Haren Coll. (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 Coll.). 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, 1 1 -jointed antennae, 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 is not so clearly 

 referable to G. hoeniesi 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 

 DimorpJiomyrtnex that have since come to light. Unfortunately this 

 question cannot be settled till 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 dwindles 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 



