On the next day I returned her to the nest, and again she was met by the indignant police at the door and conducted away. With her strong mandibles she could have crushed any number of her small assailants, but in no instance did she show the least disposition to rebel against the indignities to which she was subjected. She was often dragged away with her back on the ground and her legs coiled up, apparently helpless. If all the soldiers had been treated in this way, it would not have been so remarkable, but so far as I could see the rest were allowed to remain, going in and out of the nest as if taking a survey of their new surroundings.
For five months I had these ants under almost constant observation, and yet I was unable to make out the true position of the soldiers in the colony. They stay mostly within the nest. On the warmest days a few will come out and walk leisurely around the mound. They are not scattered irregularly through the nest, but seem to be housed together in large chambers. In one of these chambers I found a wingless queen in their midst. It seemed very fitting for a queen to be surrounded by Amazon soldiers; but, alas! they seemed more like maids of honor than soldiers, for they forsook the royal lady without making an effort to defend her. Not so, however, with the little workers: they rallied around her, ready to guard her with their lives, and no doubt would have succeeded had it been any ordinary foe.
This phenomenon—the soldiers and queens with smooth mandibles—is very puzzling, and has excited much interest among naturalists both in this country and in Europe. I sent specimens to Mr. Charles Darwin, which he forwarded to Mr. Frederick Smith of the British Museum (who, Mr. Darwin informs me, is the highest authority in Europe on ants and other Hymenoptera). Mr. Smith says: "Your observations on the structural differences in the mandibles of this ant are quite new to me." I also sent specimens to the eminent naturalist Dr. Auguste Forel of Munich, who, like Mr. Smith, had never observed this feature of the mandibles in any ant; but he has a theory to account for it—that the smooth mandibles have been worn down by labor. If this theory is true, how can we account for the fact that other ants do not wear down their teeth? The chitinous covering of this harvesting-ant is firm and hard. The stage forceps of my microscope closes with a spring, and in studying this ant I have put thousands of individuals to the test, holding them in the forceps to examine their mandibles, and in no instance do I recollect seeing one injured, while many other species are easily injured by the forceps. Among these are the two large species of carpenter-ant before mentioned, which work in stumps or fallen timber. These ants all have well-developed teeth, and the shell-like covering enveloping the body is much thinner than that of the harvesting-ant.
If it be urged that hard wood will not wear down the teeth like mining in the sandy soil, I can bring forward another member of this family (Camponotus socius, Roger), which lives in the ground, and whose mining and tunnelling are on a much more extensive scale than those of the harvesting-ant. The formicary of this Camponotus often extends over several square rods, with large entrances at various points, all connected by underground galleries, requiring a great amount of labor to construct them; while each colony of the harvesting-ant has a close, compact nest or formicary, requiring much less work to construct it. The worker major of Camponotus socius is very large—larger than the soldier of the harvesting-ant. The formicaries of the two species are often in close contact, so that the nature of the soil is precisely the same. I have examined thousands of Camponotus socius, and in no instance have I found the teeth worn down.
There is still another difficulty in the way of Dr. Forel's theory. Careful observations have revealed the fact that all the harvesting-ants that engage in work of any kind are armed with teeth. I took thirty soldiers with smooth mandibles, put them in a glass jar with every facility for making a nest, but they refused to work, scorned all my offers of food, and remained huddled together for three days. I then introduced several workers minor, and they immediately commenced tunnelling the earth and making chambers, into which the lazy soldiers crawled, meeting with no opposition from these industrious little creatures. My experiments did not stop here. I now took about a hundred specimens—soldiers and a few workers major, the last with partially-developed teeth—and placed them in a jar. Some of these made feeble attempts to construct a nest, but they did not store away seeds, and larvæ which I put in the jar they carried about as if not knowing what to do with them.
There is every appearance of an aristocracy among these humble creatures. The minors are the servants who do the work, while the queens and soldiers (especially the soldiers, which more nearly approach the queen in shape of head and mandibles) seem to live a life of comparative ease, and have their food brought to them by the minors. This may be the reason of the non-development of the teeth among the aristocracy. But how the same parent can produce such differing offspring—some born to a life of ease, with obsolete teeth, and others with well-developed teeth to do the work—is one of the mysteries in Nature. The only way to settle the point with regard to the mandibles beyond dispute is to find the pupæ of very young queens and soldiers, which I was unable to do during my stay in Florida. All the young were in the larval state.
Mary Treat.
DOCTEUR ALPHÈGE.
"MARCELLINE! Marcelline! viens m'aider: je souffre!"