]22 William Mortox Wheeler 



and coloration. The color variation, which ranges from black through 

 brown and red to yellow, is probably largely due to preservation, but it 

 is not impossible that several color varieties were already in existence 

 in the Lower Oligocene. 



That the species of Lasius of this age were already supporting 

 myrmecophilous mites is shown by two workers in the Geolog. Inst. 

 Koenigsberg Coll. (B 5345 and B 5187), each of which bears a large 

 Gamasid attached to the ventral side of the base of the left hind tibiae. 

 The close similarity in the position of the two specimens suggests that 

 these mites had already acquired the habit so remarkably developed 

 in some of the recent species of Antennophorus and Cillibano, of 

 attaching themselves to very definite regions of their host's body. 



Lasius pumilus Mayr. 



Lasius pumilus Mayr, Beitr. Naturk. Preuss. J, 1868, p. 46, Taf. II, Fig. 33 $; Dalla 

 Torre, Catalog. Hymen. VII, 1893, p. 190; Ern. Andre, Bull. Soc. 

 Zool. France, XX, 1895, p. 82; Handlirsch, Foss. Insekt. 1908, p. 860. 



Only the worker of this species was described by Mayr, and 

 notwithstanding much search I have been unable to find the male and 

 female in the material under observation. The worker is extremely 

 small for a Lasius, measuring, according to Mayr, only 1,5 mm. Some 

 of the specimens I have seen are even smaller (1,25 mm). The terminal 

 joints of the maxillary palpi are long and subequal as in L. schieffer- 

 deckeri and the recent niger and show no tendency to decrease in 

 length distally as in the fiavus and umbratus forms. The species can 

 be readily distinguished from schiefferdeckeri not only by its size but 

 by the pilosity and the much shorter antennal joints. Joints 2 — 4 of 

 the funiculi are distinctly broader than long and the remaining joints, 

 except the last, are scarcely longer than broad. The erect hairs are 

 absent on the head, thorax and appendages and are present only on 

 the gaster, and especially at its posterior end where they are long, 

 sparse and delicate. The epinotum is shorter than in schiefferdeckeri 

 and the petiole is rather high and obovate when seen from behind, 

 with a rather sharp and, in some specimens, feebly emarginate superior 

 border. The various specimens show the same range of actual color 

 variations as schiefferdeckeri. 



Mayr based L. pumilus on three specimens, one of which (7511/225) 

 is still in the Geolog. Inst. Koenigsberg Coll. I have seen also 67 other 

 specimens which I refer to this species, 58 in the Geolog. Inst. Koenigs- 

 berg Coll. (B 18 891, XXB 754, B 18157, XXB568, XXB 758, B 18941, 

 XXB 724, B 5447, B 19 708, B 603, B 18 905, XXB 512, B 18 784, 



