Fig. 61—Head of Polyergus rufescens. (After André.)
Polyergus rufescens, an European ant allied to Formica, is renowned since the time of Huber (1810) as the slave-making or Amazon ant. This creature is absolutely dependent on its auxiliaries for its existence, and will starve, it is said, in the midst of food unless its servitors are there to feed it. Wasmann, however, states that Polyergus does possess the power of feeding itself to a certain extent. Be this as it may, the qualities of this ant as warrior are superb. When an individual is fighting alone its audacity is splendid, and it will yield to no superiority of numbers; when the creatures are acting as part of an army the individual boldness gives place to courage of a more suitable sort, the ants then exhibiting the act of retreating or making flank movements when necessary. If a Polyergus that is acting as a member of a troop finds itself isolated, and in danger of being overpowered, it has then no hesitation in seeking safety even by flight. This species is provided with mandibles of a peculiar nature; they are not armed with teeth, but are pointed and curved; they are therefore used after the manner of poignards, and when the ant attacks a foe it seizes the head between the points of these curved mandibles, and driving them with great force into the brain instantly paralyses the victim.
Mandibles of this shape are evidently unfitted for the purposes of general work, they can neither cut, crush, nor saw, and it is not impossible that in their peculiar shape is to be found the origin of the peculiar life of Polyergus: we find similar mandibles reappearing amongst the aberrant Dorylides, and attaining a maximum of development in the ferocious Eciton; they also occur, or something like them, in a few aberrant Myrmicides; and in the male sex of many other ants, which sex exercises no industrial arts, this sort of mandible is present.
The ants that Polyergus usually attacks in order to procure slaves are Formica fusca and F. fusca, race auricularia; after it has routed a colony of one of these species, P. rufescens pillages the nest and carries off pupae and some of the larger larvae to its own abode. When the captives thus deported assume the imago state, they are said to commence working just as if they were in their own houses among their brothers and sisters, and they tend their captors as faithfully as if these were their own relatives: possibly they do not recognise that they are in unnatural conditions, and may be quite as happy as if they had never been enslaved. The servitors are by no means deficient in courage, and if the place of their enforced abode should be attacked by other ant-enemies they defend it bravely. The fact that P. rufescens does not feed its larvae has been considered evidence of moral degeneration, but it is quite possible that the Insect may be unable to do so on account of some deficiency in the mouth-parts, or other similar cause. The larvae of ants are fed by nutriment regurgitated from the crop of a worker (or female), and applied to the excessively minute mouth of the helpless grub: for so delicate a process to be successfully accomplished, it is evident that a highly elaborated and specialised arrangement of the mouth-parts must exist, and it is by no means improbable that the capacity of feeding its young in true ant-fashion is absent in Polyergus for purely mechanical reasons.
M‘Cook states that the North American ant, Polyergus lucidus, which some entomologists consider to be merely a variety of the European species, makes slaves of Formica schaufussi, itself does no work, and partakes of food only when fed by its servitors. He did not, however, actually witness the process of feeding. When a migration takes place the servitors deport both the males and females of P. lucidus. M‘Cook adds that the servitors appear to be really mistresses of the situation, though they avail themselves of their power only by working for the advantage of the other species.
Fig. 62—Myrmecocystus mexicanus. Honey-pot ant, dorsal view.
Fig. 63—Myrmecocystus mexicanus. Lateral view.