A Text-book of Entomology: Including the Anatomy, Physiology, Embryology and Metamorphoses of Insects for Use in Agricultural and Technical Schools and Colleges as Well as by the Working EntomologistPackard, A. S. (Alpheus Spring)
Science
A Text-book of Entomology: Including the Anatomy, Physiology, Embryology and Metamorphoses of Insects for Use in Agricultural and Technical Schools and Colleges as Well as by the Working Entomologist
Packard, A. S. (Alpheus Spring)
Insects
The gustatory organs of insects are microscopic pits or setae, either
hair-like or resembling short pegs, which form the ends of ganglionated
nerves. They are difficult to distinguish morphologically from certain
olfactory structures, and it is owing to their position at or very near
the mouth that they are supposed to be gustatory in nature.
Meinert was the first (1860) to suggest that organs of taste occurred in
ants. He observed in the maxillæ, and tongue of these insects a series
of canals in the cuticula of these organs connected with ganglion-cells,
and through them with the nerves, and queried whether they were not
organs of taste. Forel afterwards (1874) confirmed these observations.
Wolff in an elaborate work (1875) described a group of minute pits (Fig.
284) at the base of the tongue of the honey bee, which he supposed to
possess the sense of smell, but Forel and also Lubbock attributed to
these sensory pits the function of taste. Ten years afterward Will
showed conclusively, both by anatomical studies and by experiments, that
Diptera and Hymenoptera possess gustatory organs. He, however, denied
that the organs of Wolff were gustatory, and maintained that organs of
smell were confined to the maxillæ, paraglossæ, and tongue. As we shall
see, however, what appear to be with little doubt taste-pits, with hairs
or pegs arising from them, are most numerous on the epipharynx of nearly
all insects, and situated at a point where they necessarily must come in
contact with the food as it enters the mouth and passes down the throat.
[Illustration:
FIG. 284.—Taste-pits on the epipharynx (_C_) of the honey-bee: _B_,
horny ridge; _R_, _R_, taste-pits; _L_, _A_, _A_, muscular fibres;
_S_, _S′_, _a b c d e f_, section of skin of œsophagus.—After Wolff.
]
[Illustration:
FIG. 285.—Tip of the proboscis of the honey bee, × 140: _L_, terminal
button or ladle: _Gs_ taste-hairs; _Sh_, guard-hairs; _Hb_, hooked
hairs.—After Will.
]
Kraepelin (1883) discovered taste-organs on the proboscis of the fly,
and taste-hairs at the end of the tongue of the humble-bee (Fig. 285),
and afterwards Lubbock critically discussed the subject, and concluded
that the organs of taste in insects are situated “either in the mouth
itself, or on the organs immediately surrounding it.”
=Structure of the taste-organs.=—The organs have been best studied by
Will, who, besides describing and figuring the chitinous structures,
such as the pits or cups, hairs and the pegs, showed that they were the
terminations of ganglionated nerves.
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