312 FORMICIDjE. 



Genus MYRMECOCYSTUS. 



Formica, pt., Fair. Mant. Ins. \ (1787), p. 308, $. 

 Myrraecocvstus, Wenrn. Hull. Acad. Sc. Brux. v (1838), p. 770. 

 Cataglyplns, Font. Verh. Nat. Yer. Prcms. Itheinl. vii (1850), p. 40:T, 



Type, M. mettigera, Llave. from America. 



Iianf/e. Both hemispheres. 



. Head without the mandibles quadrangular, not emarginate 

 posteriorly, the sides straight or very slightly convex ; mandibles, 

 comparatively large, strongly dentate, the apical tooth remarkably 

 long, curved and acute ; maxillary palpi G-jointed, very long, the 

 '3rd and 4th joints the longest, the latter twice as long as the 5th 

 and arched ; labial palpi 4-jointed as in Formica clypeus convex. 

 its anterior margin slightly arched ; frontal area triangular, with 

 the clypeal-frontal suture distinct ; antenna! carinie very short, 

 parallel ; antenna) springing from immediately behind the posterior 

 border of the clypeus. 12-jointed, filiform ; eyes of moderate size, 

 oval, placed well above the middle line of the head ; ocelli present. 

 Thorax viewed from the side constricted in the middle, saddle- 

 shaped, the sutures well-marked ; pronotum convex ; mesonotum 

 long, narrow, rounded above : metanotum short, gibbous ; legs 

 long and slender. Pedicel one-jointed, node rounded, not much 

 raised ; abdomen somewhat short, oval, capable in the typical 

 species, which is American, of immense dilatation. 



2 . Similar to the Wings short, hyaline, the nervurea 

 thick, with one cubital and one small, frequently incomplete, 

 discoidal cell. 



c? . Head smaller than in the $ ; mandibles narrow, indistinctly 

 bidentate; antenna? 13-jointed, the scape long. Thorax com- 

 pressed ; pronotum slightly concave in the middle. Node of the 

 pedicel quadrangular ; abdomen cylindrical. Genitalia very large, 

 the pencili wanting, but the lamina) present : the external genital 

 plate bearing an appendix on the inner side. 



Only a single species ( only known), that differs slightly but 

 constantly from the European and North African form, is found 

 within our limits. 



&52. Myrmecocystus setipes. Ford. 



Myrmecocystus viaticus, race setipes, Forel. Jour. Jioml. N. H~ 

 ' Soc. vii'i (1894), p. 401, $. 



$ . Head, thorax, legs and node of pedicel dark red, abdomen 

 black; the legs of a darker shade than the thorax, almost black - 

 Pilosity on the head, thorax and abdomen sparse, confined to a 

 few scattered erect hairs, most numerous on the underside of the 

 abdomen ; legs densely setose and spinous ; pubescence extremely 

 minute and fine, with a silvery glint, but giving the. head, thorax 

 and abdomen a dull subopaque appearance. For the rest the 

 characters of the genus. 



Lcnytli, % 10-12 mm. 



