252 PROCEEDINGS OF THE ACADEMY OF [Feb., 



the queen to pass, so that she remains imprisoned. With the growth 

 of the colony the chamber formerly made and inhabited by the Hol- 

 caspis larva is enlarged by the workers. The queen with the larvae 

 prefers to inhabit the small central capsule in which the Holcaspis 

 passed its pupal life. The larvae are of a peculiar greenish tint. The 

 males and virgin females make their appearance in the colony during 

 the last week of May. At no time are the colonies of L. obturator very 

 large. They rarely comprise more than 36 or 40 workers. Members 

 of different colonies, even from galls on the same branch, are extremely 

 hostile to one another. Along the creek-bottoms near Austin, L. 

 obturator is also occasionally found nesting in the twigs of the wafer- 

 ash (Ptelea trijoliata) which have been hollowed out by tiny carpen- 

 ter-bees {Ceratina nanula Ckll. and C. arizonensis Ckll.). The 

 relatively large entrance made by the bees at the end of the twig is 

 plugged up by the ants with agglutinated vegetable particles and 

 then perforated with a minute opening in the center. 

 16. Leptothorax nevadensis sp. nov. 



Worker (PI. XII, fig. 20).— Length 2.5-3 mm. 



^landibles 5-toothed. Clypeus depressed in the middle, its an- 

 terior margin sinuately excised. Antennae 12-jointed, scape reaching 

 to posterior corner of the head, first funicular joint as long as joints 

 2-4 together, joints 2-6 slightly broader than long, joints 7 and 8 as 

 long as broad; two basal joints of club subequal, together shorter than 

 the terminal joint. Thorax above in front of about the same width 

 as below and behind; humeri much rounded, dorsum flattened in pro- 

 file, without mesoepinotal constriction. Epinotal spines robust, 

 pointed, decidedly longer than broad at their bases, and nearer together 

 at their bases than long, directed upward, outward and backward. 

 Petiole H times as long as broad, sides of node rounded, broader than 

 the peduncle; seen from above the node is transverse, in profile it is 

 narrow antero-posteriorly, its anterior slope gently ascending, concave, 

 its posterior slope more abrupt, also concave, summit rounded; ventral 

 surface of petiole with a prominent, compressed, downwardly directed 

 tooth. Postpetiole in profile with a prominent, sometimes sHghtly 

 angular node; the segment seen from above is transversely elliptical, 

 about half again as broad as long, its anterior angles rounded. Gas- 

 ter and legs of the usual conformation. 



Mandibles striate and punctate. Clypeus subopaque, its surface, 

 especially at the sides, traversed by rather coarse longitudinal rugse. 

 Head with a satiny luster, sparsely punctate and with dehcate longi- 

 tudinal rugae, which become decidedly reticulate in the antennal 



