DAIRIES AND GUESTS
The peculiar symbiotic relations between ants and aphids is worth a
brief description. The aphids or plant-lice live in colonies upon
certain plants, and feed upon juices which they suck from the foliage.
The liquid excrement of these insects is sweet, and a surprisingly
large amount is voided--Bŭsgen found that the maple aphid produces
as many as forty-eight drops in twenty-four hours. This substance is
sometimes so abundant that it covers the leaves and even drips down to
the ground; it is known as honeydew, and some rustics still believe
that it somehow falls from heaven. The ants are very fond of this
honeydew, and some species live upon it almost exclusively at certain
seasons, and locate their nests always near good aphid-pastures. The
ants never kill and eat aphids as they do other insects, but protect
them against their enemies. They even carry them about from one pasture
to another, and some species build little sheds and corrals in which
their aphids are confined just as we confine cattle. Sometimes the ants
simply lap up the honeydew as it falls upon the leaves, but in most
cases they _milk_ the aphids by gently stroking them with the antennae,
which causes the emission of a drop of the sweet liquid. Some kinds of
aphids have developed a circle of stiff hairs around the anal opening,
which thus retains the honeydew till the ant comes for it. Not only do
the ants care for and milk the adult aphids, but they rear them from
the eggs. Huber, Lubbock and others have seen ants collecting aphid
eggs in the Autumn, and it has been found that these eggs are stored in
the nest until they hatch, when the young plant-lice are carried out
and placed on a suitable food-plant. On cold or rainy days they are
taken back into the nest; when the weather moderates the ants carry
them out to pasture again.
The scale-insects and mealy-bugs (_Coccidae_) also produce honeydew,
and are visited by the ants precisely as the aphids are. The _manna_
of the Biblical story, according to Wheeler, “is now known to be the
honeydew of one of these insects (_Gossyparia mannifera_) which lives
on the tamarisk. This excretion is still called _man_ by the Arabs who
use it as food.” Forel, Cockerell and Wheeler have seen ants tending
great herds of coccids, and a few of these insects are found in many
nests.
Several kinds of tree-hoppers bear a similar relation to ants. Bare,
who studied these matters in Argentina, “watched the larvae of various
species of _Centrotus_ being assiduously attended by ants. The larvae
are gregarious, frequenting the succulent shoots of plants, and have an
extensile organ at the extremity of the body, from which the coveted
fluid is emitted.” Wheeler observed whole colonies of ants herding
leaf-hoppers in Colorado, and reports that these novel milk-cows
“responded to the antennal caresses of the ants in precisely the same
manner as the plant-lice and scale-insects.” Some ants confine their
tree-hoppers in sheds and shelters similar to those used for the aphids.
The relationship of ants to certain small caterpillars (the larvae
of some of the _Lycaenid_ butterflies) has been known for a long
time. These little caterpillars, when caressed on the posterior
end by the antennae of the ants, give up a drop of sweet liquid,
doubtless very similar to that produced by the aphids and coccids.
These larvae are often found in the ants’ nests, and some of the newly
emerged butterflies have been seen to come out of the ant-hills.
It is said that the ants protect the caterpillars from the attacks
of hymenopterous parasites, and De Niceville is authority for the
statement that the butterfly will not lay her eggs when there are no
ants about: “If the right plant has no ants, or the ants on that plant
are not the right species, the butterfly will lay no eggs on that
plant. Some larvae will certainly not live without the ants, and many
larvae are extremely uncomfortable when brought up away from their
hosts or masters.”
[Illustration: Fig. VI. A small myrmecophilous cricket (_Myrmecophila
nebrascensis_) gnawing at the tibia of the Texan harvester-ant. (After
Wheeler.)]
Besides the ants’ relationship with the insects which produce sweet
substances, there are symbiotic relations of a very different type with
a group of insects known as _myrmecophiles_--ant-guests. These insects,
at one stage or another, live in the ant-hills. At least fifteen
hundred species of ant-guests are known, and Escherich estimates that
there must be at least three thousand altogether. Wheeler thinks that
even this estimate is probably too low. At least a thousand of the
known species are beetles, and most of the rest are insects of one kind
or another, but there are about sixty arachnids and a few crustaceans.
Some of the myrmecophiles are not _friends of ants_ as the name
implies, but mere interlopers--scavengers, robbers and assassins.
There are a number of small beetles which live in the less frequented
galleries of the nest, eat dead ants and brood, kill ailing or crippled
ants, and even attack healthy adults when they catch them alone or
at some disadvantage. Some of these beetles resemble ants in general
appearance, a mimicry which is doubtless of considerable value to
them. The ants kill these pests whenever they can, but many are
protected by their ability to emit an evil-smelling substance which
puts the ants to flight. Others will be killed at once if confined in a
small chamber with a few ants, but in a large nest are able to escape
by reason of their agility.
Another class of myrmecophiles, known as _synoeketes_, or tolerated
guests, live in the ant-hills without attracting any great attention,
being treated with contemptuous indifference by their hosts. The larvae
of certain moths and flies, a large number of beetles, and numerous
other insects are of this class, and feed largely upon the refuse of
the kitchen-middens. Wasmann has studied a group of beetles which
live with the nomadic Doryline ants. These camp-followers mimic the
legionaries, and march along in their columns apparently unnoticed,
being allowed to share the prey taken by the blind warriors. Other
beetles live in the nests of the _sanguinea_, and feed largely upon the
tiny parasites from the bodies of their hosts. Certain minute wingless
crickets are very abundant in many nests; they are seen to lick the
bodies of the ants, and it is supposed that they live upon some
cutaneous secretion.
The insect called _Attaphila_ is a sort of miniature cockroach, which
lives with the fungus growing _Attii_, and is, according to Wheeler,
the only insect known to be on intimate terms with these ants. A
peculiar thing about the _Attaphila_ is that the last joint of the
antennae is nearly always bitten off. This insect was formerly
supposed to feed on fungus, but has since been found to lick the
surface secretions from the ants’ bodies. A little beetle called
_Oxysoma oberthueri_ is very like _Attaphila_ in its habits, “mounting
the bodies of its host and licking or shampooing them with great
eagerness.”
Very different from the furtive, barely tolerated myrmecophiles
described above are the three or four hundred species known as true
guests, which, to quote Wheeler again, “are no longer content to be
treated with animosity or indifference, but have acquired more intimate
and even friendly relations with the ants. These true guests are not,
therefore, to be found skulking in the unfrequented galleries of the
nest, or suspiciously dodging about among the ants, but live in their
very midst with an air of calm assurance, if not of proprietorship.”
Among these are many beetles bearing tufts of hair which produce some
aromatic secretion very pleasing to the ants. The ants rush to lick the
odorous tufts, are caressed by the peculiar antennae of the beetle,
and feed the latter with regurgitated food. Many of these beetles are
cleaned and shampooed by the ants, are often carried about, and favored
in other ways, despite the fact that they sometimes devour the ant
brood. Some of the smaller species are totally blind, and are permitted
to ride about on the ants’ backs for hours at a time.
Another sort of guest is the little mite called _Antennophorus_,
which Janet has found in the nests of several European ants. These
mites attach themselves firmly to the body of their host, and it is
interesting to note that no matter how many are present on a single
ant, they are always so placed that the weight is properly distributed,
and the host’s progress not interfered with. These creatures remind
one of the ticks found on higher animals like dogs, but they are not
parasites in the sense that ticks are--they do not suck the ant’s
blood, but reach out and snatch their nutriment from the drops of
regurgitated food as they pass from one ant to another.
[Illustration: Fig. VII. Showing two minute myrmecophilous beetles
(_Oxysoma oberthueri_) feeding on the surface secretions of an ant.
(Adapted from Escherich).]
The ants do not bother _Antennophorus_ much, but there is another mite
called _Cillibano_ which is a true blood-sucker, and which they seize
and tear to pieces whenever they can. A little blue fly (_Orasema
viridis_) is common in the nests of several Texan and Mexican ants; its
larvae attach themselves to the ant larvae and live as parasites. Both
the larvae and the adult, however, are fed and fondled by the ants.
Besides these external parasites there are many grubs and worms which
live inside the body of the ant, and are comparable to the pin-worms
and tapeworms which dwell in the human intestine. These creatures have
not been studied extensively, however, and very little is known of
their habits and metamorphosis.
* * * * *
Transcriber’s note
Minor punctuation errors have been changed without notice. Italization
was standardized.
Illustrations tags have been moved so they do not break up the
paragraphs.
Spelling was retained as in the original except for the following
changes:
Page 7: “female during copulalation” “female during copulation”
Page 17: “the arangement of larvae” “the arrangement of larvae”
Page 18: “the ant’s tevelopment” “the ant’s development”
Page 29: “habits of the Attiine” “habits of the Attine”
Page 29: “besides the Attiien ants” “besides the Attine ants”
Page 44: “itself every reason to” “itself every season to”
Page 50: “of several _sanquinea_” “of several _sanguinea_”
Page 51: “the _sanquinea_ queen” “the _sanguinea_ queen”
Page 55: “is known as honey dew” “is known as honeydew”
Page 55: “honey dew, and some species” “honeydew, and some species”