The nests are composed of a variable number of
chambers, of irregular shape, connected by gal-
leries. They are excavated in the ground, often
under the shelter of a stoue, or in rotting or liv-
ing trees, shrubs or herbs. Those chambers and
galleries excavated in the earth extend a consid-
erable distance down to the region of constant
moisture. !Some of the saiiija or saliva ants of
South America can cross wide rivers by tunneling
under the river-beds. Xot infrequently the nests
are carried above the level of the ground by
means of earth heaped up and often cemented to-
gether. Some ant-hills are. thatched by bits of
herbage. In South America ant-hills often ex-
ceed the height of man. Some ants tunnel out
homes in the trunks of trees, others burrow in the
thorns or petioles of leaves. Certain ants make
homes by bending leaves in circles. The adult
ants cannot produce cement, so the larvic nearly
ready for the cocoon stage are utilized. Some of
the workers hold the bent edges of the leaves in
place, while others bring up the larvfE, whose
heads they dab back and forth over the edges of
the leaves so as to bind them together with silk.
Symbiosis. Although certain ants are very
destructive to vegetation, the relationship be-
tween ants and certain plants is sometimes one of
mutual advantage, a symbiotic one. Thus, in
South America, there is a small acacia known as
the bull's-horn thorn, on account of the paired,
horn-shapeil tliorns l)orne on the tree. While the
thorns are still young the ant jjierces a hole in
the tip of one of them and then makes its way
lljrough the thorn to tlu' base, where it tunnels
into the other thorn. Within the thorns there is
a sweet pul]) eaten by the ants. Those thorns
that are not entered bj- the ants shrivel and fall
oil'. At the base of each young bipinnate leaflet
on this same tree there is a honey-secreting gland,
and at the tip a minute, pear-shaped fruit. The
fruit does not all ripen at the same time; hence
(he ants (I'seudomyrma) are kept continually
running over the tender foliage in search of edi-
ble stages. 'lien the tree is disturbed, the ants
swarm out of their nests in the thorns, and by
their severe sting drive off intruders, such as
caterpillars and even vertebrates. But they are
most valuable to the tree in warding otV the leaf-
cutting ants that in a few hours can defoliate a
tree. In the leaf petioles of another plant (Mel-
astoma) there are two pouches. In Ihese ants
find homes, and, in return, they keep oft' the leaf-
cutting ants and foliage-eating foes. The young,
tender leaves of certain orchids and passion-flow-
ers have honey-glands visited by ants to the ex-
clusion of all marauders.
Eel.vtioxs of Differext Species to One An- other. Almost all kinds of ants carry off the larva- and pup* of other kinds of ants for food. At times, doubtless, more are taken than can be consumed; hence some of the captives come to maturity in the foreign nest. Perhaps in some such way as this, out of the instinct of the rob- ber ant arose that of the slave-making ant. Slave-making ants, which are lighter in color than their captives, go forth in armies, attack the nests of the black ants, and carry away the larvoe and pupae. These they bring up to act as ser- vants or slaves. In some cases the warriors are structurally unable to take food, and hence are wholly dependent on their faithful domestics, who collect the food and actually jMit it in the mouths of their captors. Other small ants (Sol- enopsis) live the lives of thieves, secreted in small chambers excavated in the interspaces between the chambers of large ants. The small entrances to the small chambers will not admit the large ants. Hence the small thieves retreat in safety to their lioraes with the young of the large ant, which they take for food. VVith the Formica tufa a small ant lives, api)arently, in pcifect harmony, ])erhaps as a domestic pet. Vlien the iormic;c arc obliged to move, the small forms go, too, tapping antenna' with them, or even riding on the backs of their hosts. Many mites (gammasids) and other little creatures are usually present in ants' nests, and seemingly on terms of friendship.
Intelligence of Ants. Ants are sensitive to sound-waves, even outside of human range; they are also keenlj' sensitive to changes in moisture and temperature. When a captive colony was jjlaced by an experimenter near the fire, the heat was so grateful to its members, says he, that "They embraced each other, and skipped and danced like playful lambs or kittens." Many cases of ants indulging in what seems to us to be sportive exercise or play are recorded. Their care for the cleanliness of the glowing young and the promptness with Ahich they remove the dead and bury them sliows a sanitary instinct. The eiimplete and apparently willing sujipression of the individual for the good of the colony almost surpasses man's comprehension of self-abnegation. The law of division of labor rules among ants. Certain groups of individuals perform only cer- tain labors. Labor-sa^•ing devices are known to ants, for groups of workers will procure and drop food or building stufl's to waiting companions be- low and thus save nuieh labor of transportation. They show ingenuity in building bridges, and may even span gaps by means of a rope made up of their own living bodies linked together. Jlore- over, theie is little doubt in the minds of ant- observers that ants connnunicate with their fel- lows. The imparting of information seems to be done by means of the antenna", which they cross and rub together. They show gi-eat solicitude for injured and hel])less companions. Information relative to the plight of unfortunate members is in some way comnmnicatcil by the discoverer to others, and a rush is made to the rescue. Fallen dt'bris is removed from the partially buried one, or the wayfarer is lifted out of pitfalls. Ants are able to recognize tlie myriads of members of their own colony, including their slaves, and even those that have been taken away in infancy. All these facts and many others convince us that ants in some manner communicate with their com- panions. Otherwise, how are the discovery and the whcrealjouts of food too large for removal by one made known to the others ; how is the intel- ligence of a mishap to a luckless companion and the necessity for aid communic.ited by the discov- erer to others; or how -ire cannibalistic and slave- making wars so managed that the whole fighting comuuinity is ready to go out simultaneously?
Oeolocic.l Antiqitty. Geologically, ants arc among the earliest Hymenontera. In Tertiary times they were, perhaps, the most abundant of all the insects, and thousands of ancient speci- mens have been found in amber.
Bibliograpahy. Mayr, "Die Formiciden der . . . Nordamcrika," I'eWiaHrf/iow/ (Zoo/of/i.sr/ic(i Botanisclieii (J csellschaf t (Vienna, 188U, pp. 41y- 4(U) ; Emery, "Nordamerikanische Anieisen- fauna," Zooloqisches Jahrhuch. Volume VII pp 633-82; Volume VIII., pp. 257-300 (Jena, 18'J.l-
