AMERICAN HYMENOPTERA. 281 



casting it into the gutter. It was interesting and indeed amusing 

 to observe the behavior of the little creature in this act. Havino- 



o 



reached the edge of the curbstone, she would rear upon her hind legs, 

 poise herself a moment thus, and bending forward, release or cast 

 the chip from her jaws. Sometimes a rapid motion of the fore legs 

 against the face followed, as though to clear the mandibles of any 

 remaining particles of sawdust. A gentle breeze that was blowing 

 lifted up the ejected cutting and carried it a greater or less distance 

 down the gutter which for several feet was strewn with the chippings. 

 Under numerous observations, the worker almost invariably assumed 

 the ramparat posture when "dumping" her load of lumber. The 

 economy of this instinct of carriage is probably something more than 

 a mere habit of cleanliness. It may have regard primarily to the 

 safety of the insect, in removing from the vicinity of its dwellino- 

 such conspicuous signs of its presence. The amount of wood exca- 

 vated during a day is, relatively considered, enormous. The instru- 

 ments by which this work is done are the mandibles, [PI. IV, fig. 6, f,] 

 stout, subtriangular organs, set in the extremity of the face. They 

 are black, serrate, convex externally, concave within like the palm 

 of the human hand. There are five strong teeth, the outer one being 

 the longest and sharpest, and having an inclination from the face, the 

 inner one rather blunt, with inclination toward the face. The muscles 

 by which these organs are moved must be very powerful to admit of 

 such results. I had conjectured that they may allow a vertical as 

 well as lateral motion, so that the mandibles act as saios as well as 

 iici-aj)ers. It is probable, however, that for the most part the wood is 

 scraped off. The general appearance of the architecture, the organism 

 of the jaws, and observations upon insects enclosed in boxes, point to 

 this conclusion. The external figure of this mandible raises some- 

 thing more than a suggestion of the hand or claw of vertebrate ani- 

 mals. A thorough anatomical analysis of it under the microscope, if 

 undertaken by some competent person, might show striking analogies 

 in structure. Only the female and the worker (which is indeed an 

 undeveloped female), have this toothed formation of the mandible; 

 that of the male [PI. IV, fig. 6, h,] is club-shaped and smooth, evidently 

 disqualifying him for labor or defense. It is a remarkable faet that 

 what may be called by analogy, "the moral qualities" of insects are 

 possessed well nigh exclusively by the female. The period of activity, 

 or perhaps of greatest activity, in this work of excavation is from the 

 middle of June to the middle of July. My own observations at least 

 would lead to this inference. This period, therefore, probably marks 

 the time when the necessities of the nursling ants, or the prospective 



TRANS. AMER. ENT. SOC. V. (36) DECEMBER, 1876. 



