32 2 Bulletin American Museum of Natural History. [Vol. XXI, 



Emery was under the impression that there were two species of 

 Liometopum in North America, L. apiculatum. Mayr, originally de- 

 scribed from Mexico, and L. microcephalum Panz. var. occidentale 

 Emery from California. Both of these forms are very closely related 

 to the typical European species and he was undoubtedly right in con- 

 sidering the relationship especially close in the case of occidentale, 

 since this form has the color and sometimes also the more rounded 

 petiolar node of microcephalum. But an examination of a great 

 number of workers from many colonies shows that all our American 

 Liomeiopa agree in having a more or less pointed petiole and a very 

 different arrangement of the dense pubescence on the gaster. Emery 

 first called attention to the fact that this pubescence in occidentale is 

 parted at the median dorsal line and diverges on either side instead 

 of converging towards the median line, as in microcephalum. (Conf. 

 Fig. I a and d.) The same is equally true of the typical apiculatum, 

 and as both this character and the usually very pointed petiole are 

 common to all our American forms, including a new subspecies to be 

 described below, I do not hesitate to refer them all to Mayr's original 

 Mexican species. 



Descriptions of American Liometopa. 



Liometopum apiculatum Mayr. 



Liometopum apiculatum. Mayr, Verhandl. k. k. zool. bot. Ges. Wien, XX, 1870, 



p. 961. 5 . 

 Liometopum, apiculatum, Dalla Torre, Catalog. Hymenopt., VII, 1893, p. 163. 

 Liom,etopum apiculatum Emery, Zool. Jahrb. Abth. f. Syst., VIII, 1894, p. 



id,'^- ?• 

 Liometopum, apiculatum, Forel, Biol. Centrali Atner. Insect. Hymenopt., Ill, 



1899— 1900, p. 104. 

 Liometopum apiculatum Viereck, Trans. Am. Ent. Soc, XXIX, 1903, p. 



71. $. 

 Worker (Fig. i, a and h). — Length 2.5-6 mm. 



Mandibles with about ten teeth on the apical and four or five very small ones 

 on the basal border. Head cordate, as broad as long, in large workers some- 

 times broader than long, with broadly excised posterior border and rounded 

 sides. Clypeus somewhat bulging at the lateral corners, with a straight anterior 

 border. Frontal area very indistinct. Frontal groove lacking. Eyes in front 

 of the middle of the head. Ocelli, even in the largest workers, very small and 

 indistinct. Antennal scape curved at the base, its tip reaching to the posterior 

 corner of the head. Funiculus but slightly thickened towards the tip; all the 

 joints longer than broad, first and last joints longest, intermediate ones growing 

 shorter distally. Thorax conspicuously narrower than the head, laterally com- 

 pressed in the meso- and metathoracic regions;, in profile rather flat above, with 

 very distinct promesonotal and mesoepinotal sutures; seen from above the pro- 



