The Ants of the Baltic Amber. 119 



K 903, K 4198, K 877, K 4451, K 868 etc.), one worker in the Berlin 

 Museum and 12 workers in the Haren Coll. (200, 221, 254, 749, 1842, 

 1075, 1736, 1875 etc.). 



The two pseudogynes are interesting as showing that an anomaly 

 which today occurs most commonly in species of the genus Formica^ 

 occasionally made its appearance as far back as Lower Oligocene times 

 and in the genus Prenolepis. Emery has also described and figured 

 a pseudogynic Ca»i})0)wtus mengei from the Baltic amber {vide infra 

 p. 139). From analogy with the conditions in Formica, Wasmann 

 would probably infer that the presence of pseudogynes in the amber 

 Prenolepis and Camponotus is an indication that these ants were in- 

 fested with beetle parasites similar in habits to Lomechusa and Ate- 

 meles, but Donisthorpe has recently communicated to me reasons for 

 suspecting that the presence of pseudogynes even in Formica colonies, 

 does not always necessarily imply the presence of these myrmecophiles. 

 I have figured (Fig. 57 b) the better preserved pseudogynic P. henschei 

 which is in the Klebs Coll, (K 868). It measures only 2 mm and is 

 therefore somewhat smaller than the normal worker, as is apt to be 

 the case with Formica pseudogynes, and the curious hunched thorax, 

 which is intermediate in structure between that of the worker and 

 female, is precisely like that of the Formica pseudogyne. The specimen 

 in the Geolog. Inst. Koenigsberg Coll. (B5202) measures 2,5 mm. It 

 is badly decomposed and not visible in profile. The pro- and mesonotum, 

 however, as seen from above, are large and convex. 



Mayr did not fail to notice the very close resemblance between 

 P. henschei and the recent P. nitens of Southern Europe. This form 

 is now regarded by Emery as being merely a subspecies of the North 

 American P. imparls Say, which is, therefore, an ancient circumpolar 

 species. Although henschei is smaller than either of these recent 

 forms, there is a small variety of imparis (var. minnta Emery) in 

 Maryland, which is not larger than the fossil species. It is not im- 

 probable, therefore, that henschei is the ancestor of the present imparis. 

 This, I may state in passing, is always associated with arboreal vege- 

 tation and, in my experience, specifically with oaktrees, as one may 

 easily observe in the pine -barrens of New Jersey and the live-oak 

 groves and scrub -oak chaparral of California. It is probable that 

 henschei lived in similar association with the oaks whose common 

 presence in the amber forests is attested by the number of their 

 peculiar stellate hairs scattered through the blocks enclosing the 

 insects. 



