Chapter XVI: Part I: Morphology and Physiology (12)

Historical researches in respect to the Coleoptera generally gave a very unfavorable result, contrary to Lespès’s views. That author states that in the Carabidæ the pits are found on the four first joints, but Hauser could discover them in none which he examined. Usually only tactile bristles occur, so also in the Cerambycidæ, Curculionidæ, Chrysomelidæ, and Cantharidæ. In a blind silphid beetle (_Adelops hirtus_) of Mammoth Cave we have found well-marked olfactory organs (Fig. 274). Similar organs occur in the antennæ of the Panorpidæ.

Olfactory pits, however, without doubt occur in Silpha, Necrophorus, Staphylinus, Philonthus, and Tenebrio. The openings of the pits are small and surrounded with a small chitinous ring; in Silpha, Necrophorus, and Tenebrio they cannot easily be distinguished from the insertion-cavities of the bristles, but in Philonthus and Staphylinus they are less like them, being distinguished by their somewhat larger size and their often more oval form. In _Philonthus æneus_ about 100 such small pits occur irregularly on the terminal joints; besides, in this species on each side of the terminal joint is an apparatus which is like the compound pit generally occurring in the Diptera.

FIG. 275.—Olfactory pits of the antenna of _Melolontha
vulgaris_.—After Kraepelin.
]

FIG. 276.—Antennal pit of _Melolontha vulgaris_, seen in vertical
section.—After Hauser.
]

Very remarkable pits occur in the antennal lamellæ of _Melolontha vulgaris_ (Fig. 275) and other lamellicorns. On the outer surface of the first and seventh (in the female the sixth) antennal leaf, as also on the edges of the other leaves, only arise scattered bristles; on the inner surface of the first and seventh leaves, as also on both surfaces of the second to sixth leaves, are close rows of rather shallow depressions of irregular form, some circular, others regularly hexagonal. Their number is enormous: in the males 39,000, in the females about 35,000, occur on each antenna.

FIG. 277.—Organ of smell of Anophthalmus.—After Hauser. _A_, _a_, _b_,
the same in _A. tenuis_, _B_ in _A. tellkampfii_.
]

FIG. 278.—Section through antennal joint of _Vespa crabro_, showing
the great number of olfactory pits, olfactory and tactile bristles.
_A_, section through an olfactory pit of _Vespa crabro_.—After
Hauser.
]

The antennal pits and teeth of _Dyticus marginalis_ are morphologically and physiologically identical with those of bees and wasps. In _Anophthalmus bilimekii_, Hauser found on the last antennal joints about 60 teeth, which essentially differ in form from those previously described; they are very pale, transparent, cylindrical, elongated, and bent elbow-shaped on the first third, so that the last two-thirds run parallel with the antenna. The length of these remarkable teeth is 0.035 mm., their breadth 0.005 mm. He only found them in Anophthalmus, and in no other species of Carabidæ; they must resemble the teeth described in Chrysopa. Our species possesses similar processes (Fig. 277). Similar teeth occur on the maxillary and labial palpi of beetles. _Dyticus marginalis_ possesses at the end of each terminal palpal joint a group of very small teeth, which were also detected in _Anophthalmus bilimekii_, _Melolontha vulgaris_, etc. In _Carabus violascens_ were detected on the maxillary palpi large, plainly microscopical, white disks, which are surrounded with a great number of extremely small teeth.

Whether the above-described organs on the palpi of beetles should be considered as olfactory or gustatory in their nature can only be determined by means of physiological experiments; they probably receive taste-nerve terminations.

FIG. 279.—Olfactory pits of the antenna of _Vespa vulgaris_.—After
Kraepelin.
]

The Hymenoptera furnished very good material for histological purposes, so that Hauser could not only study the terminal apparatus of the olfactory nerves in the perfect insect, but also in three different stages of the pupa. These are described at length, as regards the distribution of the pits and teeth, in _Vespa crabro_; each joint of the antenna (flagellum) possesses between 1300 and 1400 pits, nearly 60 teeth, and about 70 tactile hairs; on the terminal joint there are more than 200 teeth, so that each antenna has between 13,000 and 14,000 olfactory pits and about 700 teeth (Kegeln). Fig. 278 represents a cross-section through the penultimate antennal joint of _Vespa crabro_; we can see how thick are the series of openings on the surface of the antennæ, and how regular is the distribution of the teeth.

The distribution of the olfactory pits and olfactory teeth is thus seen to be very general; the deviations are so insignificant that there is no reason for the establishment of more than one type.

Antennal pits with a small crevice-like opening occur in genera nearly allied to Vespa and also in most Ichneumonidæ, Braconidæ, and Cynipidæ. But the crevice-like openings in these families are considerably longer and often are of a somewhat twisted shape. In all the species with translucent antennæ we can recognize the inner mouth of the pit as a round or nearly round disk situated usually under the middle of the opening. The antennal pits of _Apis mellifica_, as well as those of Bombus (Fig. 280) and allied genera, differ from those of the Ichneumonidæ in being not like crevices, but circular openings.

FIG. 280.—Olfactory pits of the antenna of Bombus.—After Kraepelin.
]

FIG. 281.—Olfactory pits of the antenna of Formica: _Fv_, Hicks’
“bottle,” Forel’s flask-shaped organ, _Fvo_, its opening.—After
Kraepelin.
]

FIG. 282.—Supposed olfactory organs at end of antenna of Campodea:
_A_, _C. staphylinus_. _B_, _C. cookei_, from Mammoth Cave.
]

FIG. 283.—Vertical section through a single olfactory pit in the
antenna of the horse-fly (_Tabanus bovinus_). For lettering see p.
272.—After Hauser.
]

The distribution of the olfactory peg or tooth-like projections seems to be much more limited than that of the pits in the Ichneumonidæ. Hauser could not find any. _Apis mellifica_ possesses on each antennal joint only about twenty slender pale teeth, scarcely a third as many as in _Vespa crabro_; on the other hand, Formica, of which genus several species were examined, seems to have far more teeth than pits; they are relatively long, pale, transparent, and somewhat clavate; they are not unlike those of Chrysopa; on the terminal joint only occur the round openings (_Fvo_), which lead into a bottle-shaped invagination of the integument (_Fv_) and contain an olfactory style (Fig. 281). In the Tenthredinidæ only teeth and no pits were to be detected. Sirex has on the under side of the nine last joints of each antenna a group of from 200 to 300 small teeth, which resemble those of _Vespa crabro_; Lyda has on the terminal joints about 100 teeth. We may add that supposed organs of smell occur on the antennæ of Campodea (Fig. 282).

Kraepelin also thus briefly summarizes Hauser’s statements as to the forms of the different organs of smell.

The manifold nature of the antennal organs has, by Hauser, from
thorough studies of the nerve-elements belonging to them, been not
simplified but rendered more complicated. According to this
naturalist we may distinguish the following forms which the
olfactory organs may assume: 1. “Pale, tooth-like chitinous hairs on
the outer surface of the antennæ, which are perforated at the end;
nothing is known as to the relation of the nerve passing into it
(Chrysopa, Anophthalmus). 2. In pit-like depressions of the antennæ
arise _nerve-rods_ (without a chitinous case) which stand in direct
relation with a ganglion-cell lying under it. These pits are either
_simple_, viz. with only an ‘olfactory rod’ (Tabanus, Fig. 283, and
other Diptera, Vanessa), or _compound_ (Muscidæ, and most other
Diptera, and Philonthus). It is important that these pits are partly
_open_ (in the above-named groups of insects), and partly _closed_
and covered with a thin membrane, under whose concavity the
olfactory rods end (Orthoptera, Melolontha, and other lamellicorns).
3. Short, thick pits sunken slightly into the surface of the
antennæ, and over this a chitinous peg perforated at the end, in
whose base, from the interior, projects a very singular nerve-peg,
which is situated over an olfactory ganglion-cell, and provided with
a slender crown of little rods, and flanked on each side by a
flagellum-cell (Hymenoptera). 4. Round or crevice-like pits covered
over by a perforated chitinous membrane with nerve-rods like those
in 3, but in place of the flagellum-cell with ‘membrane-forming’
cells spread before it. Hauser finally mentions further differences
in the ganglion-cells sent out into the nerve-end apparatus. These
exhibit in Diptera and Melolontha only one nucleus, in Hymenoptera a
single very large one (with many nucleoli) and three small ones, in
Vanessa six, in Orthoptera a very large number of nuclei, etc.”

LITERATURE OF THE ORGANS OF SMELL

=Réaumur, Réné Ant. de.= Mémoires pour servir à l’histoire des
insectes. Paris, 1734–42. (i, 283; ii, 224).

=Lesser, F. C.= Insecto-theologia, 1740, p. 262.

=Roesel, A. J.= Insektenbelustigungen, 1746, ii, p. 51.

=Reimarus, H. S.= Allgemeine Betrachtung ueber die Triebe der Thiere
hauptsächlich ihre Kunsttriebe (Instinct). Hamburg, 1760, p. 355.

=Sulzer, J. H.= Die Kenntzeichen der Insecten. Zürich, 1761.

=Lyonet, P.= Traité anatomique de la chenille, 1762, pp. 42, 96, 195.

=Comparetti, A.= De aure interna comparata. Patavii, 1769.

=Bonnet, C.= Œuvres complètes, 1779–1783, ii, p. 36.

—— Contemplation de la nature, Ch. iii, p. 18.

=Scarpa, Ant.= Anatomicæ disquisitiones de auditu et olfactu. Ticini,
1789.

=Huber, F.= Nouvelles observations sur les abeilles, 1792, ii, p. 475.

=Lehrmann, M. C. G.= De antennis insectorum. Londini, Hamburgi, 1799,
p. 48, Diss. posterior; Hamburg and London, 1800, p. 80 (especial
sense, ærocepsis).

=Latreille, P. A.= Histoire naturelle des crustacés et des insectes,
1806–1809, ii, 50.

=Blainville, M. H. D.= Principes d’anatomie comparée, 1822, i, p. 339.

=Dugès, A. L.= Traité de physiologie comparée, 1838, i, p. 161.

=Newport, G.= On the use of the antennæ of insects. (Trans. Ent. Soc.,
London, ii, 1840, pp. 229–248.)

=Robineau-Desvoidy, A. J. B.= Sur l’usage réel des antennes chez les
insectes. (Ann. Soc. Ent. France, 1842, xi Bull., pp. 23–27.)

=Erichson, W. F.= De fabrica et usu antennarum in insectis. Berlin,
1847, 1 Tab., p. 13.

=Perris, E.= Mémoire sur le siège de l’odorat dans les articulés.
(Ann. sc. nat., Sér. 3, 1850, xiv, pp. 159–178.)

=Dufour, L.= Quelques mots sur l’organe de l’odorat et sur celui de
l’ouie dans les insectes. (Actes d. l. Soc. Linn., Bordeaux, 1850,
xvii, Ann. sc. nat., Sér. 3, Zool., xiv, 1850, pp. 179–184.)

=Leydig, F.= Zum feineren Bau der Arthropoden. (Müller’s Archiv, 1855,
pp. 376–480); Lehrbuch der Histologie, 1857, p. 220; Zur Anatomie
der Insekten (Archiv für Anatomie, 1859, pp. 35–89 and 149–183).

—— Ueber Geruchs- und Gehörorgane der Krebse und Insekten. (Archiv f.
Anat. u. Phys., 1860.)

—— Die Hautsinnesorgane der Arthropoden. (Zool. Anzeiger, 1886, pp.
284–291, 308–314, 265–314.)

=Landois, H.= Das Gehörorgan des Hirschkäfers. (Archiv f. mikrosp.
Anat., 1868, iv, pp. 88–95.)

=Troschel, H.= Ueber das Geruchsorgan der Gliedertiere. (Verhandl. d.
naturhist. Vereins d. preuss. Rheinlande u. Westfal., xxvii Jahrg.,
1870, pp. 160–161.)

=Packard, A. S.= The caudal styles of insects sense-organs, _i.e._,
abdominal antennæ. (Amer. Naturalist, 1870, pp. 620, 621. Also Proc.
Bost. Soc. Nat. Hist., 1868, xi, p. 398.)

=Paasch, A.= Von den Sinnesorganen der Insekten im Allgemeinen, von
Gehörund Geruchsorganen im Besondern. (Archiv für Naturgesch., xxxix
Jahrg., i, 1873, pp. 248–275.)

=Chadima, Jos.= Ueber die von Leydig als Geruchsorgane bezeichneten
Bildungen bei den Arthropoden. (Mitteil. d. naturwiss. Ver. f.
Steiermark, 1873, pp. 36–44.)

=Forel, A.= Les Fourmis de la Suisse. (Neue Denkschr. Allg. Schweiz.
Gesellsch. f. d. ges. Naturw., xxvi, 1874, pp. 118, 144.)

—— Études myrmécologiques en 1884, avec une description des organes
sensoriels des antennes. (Bull. Soc. Vaud. sc. nat., 1885, Sér. 2,
xx, pp. 316–380.)

=Graber, V.= Die Insekten. München, 1877.

—— Neue Versuche über die Functionen der Insektenfühler. (Biol.
Centralb., vii, 1887, pp. 13–19.)

=Trouvelot, L.= The use of the antennæ in insects. (Amer. Naturalist,
xi, 1877, pp. 193–196.)

=Mayer, P.= Sopra certi organi di senso nelle antenne dei Ditteri.
(Atti R. Accad. d. Lincei, Roma, Ser. 3, Mem. Cl. sc. fis., mat. e
natur., iii, 1879, p. 11.)

=Hauser, Gustav.= Physiologische und histiologische Untersuchungen
über das Geruchsorgan der Insekten. (Zeitschr. f. wissens. Zool.,
xxxiv, 1880, pp. 367–403, 3 Taf.)

=Kraepelin, Karl.= Ueber die Geruchsorgane der Gliedertiere
(Oster-Programm der Realschule des Johanneums. Hamburg, 1883, pp.
48, 3 Taf.)

=Schiemenz, Paulus.= Ueber das Herkommen des Futtersaftes und die
Speicheldrüsen der Bienen nebst einem Anhange über das Riechorgan.
(Zeitschr. f. wissens. Zool., xxxviii, pp. 71–135, 3 Taf.)

=Plateau, F.= Expériences sur le rôle des palpes chez les arthropodes
maxillés, I., Palpes des insectes broyeurs. (Bull. Soc. Zool.
France, x, 1885, pp. 67–90.)

=Plateau, F.= Une expérience sur la fonction des antennes chez la
Blatte (_Periplaneta orientalis_). (Comptes rend. Soc. Ent. de
Belgique, 1886, pp. 118–122, 1 Fig.)

=Lubbock, J.= On some points in the anatomy of ants. (Monthly Micr.
Journ., 1887, pp. 121–142.)

=Ruland, Franz.= Beiträge zur Kenntniss der antennalen Sinnesorgane
der Insekten. Diss. Marburg, 1888, p. 31, 1 Taf.

=Wasmann, E.= Die Fühler der Insekten. (Stimmen aus Maria-Laach.
Freiburg i. B., 1891, p. 37.)

=Sergi, G.= Ricerche su alcuni organi di senso nelle antenne delle
formiche. (Riv. Filos. Sci. Milano, 1891, p. 10, 3 Figs.)

=Nagel, Wilibald.= Die niederen Sinne der Insekten, 19 Figs.,
Tübingen, 1892, pp. 67.

With the writings of Baster, Lamarck, Cuvier, Treviranus, Oken,
Lefebure, Duméril, Schelver, Bousdorf, Rosenthal, Burmeister,
Slater, Balbiani, Marcel de Serres, Garnier, Berté, Porter, Sazepin,
Reuter, Pierret, Duponchel, Driesch, Küster, Peckham, Lubbock, A.
Dohrn, Lespès.

_c_. The organs of taste

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.

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.
]

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.

Figure 286 represents the taste-cups on the maxilla of a wasp, and Fig. 287 the taste-cone or peg projecting from the cup or pit. The cell out of which the pit and projecting hair or peg are formed is a modified hypodermis cell; and the seta is apparently a modification of a tactile hair, situated at the end of a nerve, which just beneath the chitinous structures passes into a ganglion-cell, which sends off a nerve-fibre to the main nerve.

Will detected on the tongue of the yellow ant (_Lasius flavus_) from 20 to 24, and in Atta from 40 to 52, of these structures. The number of pits on the maxillæ vary much, not always being the same on the two sides of the same insect. We have observed these taste-cups in the honey and humble bee, not only at the base of the second maxillæ (Fig. 288, _g_), but also on the paraglossæ (_pg_).

=Distribution in other orders of insects.=—The writer has detected
these taste-cups in other orders than Diptera and Hymenoptera. They
very generally occur in mandibulate insects on the more exposed
surface of the epipharynx (compare pp. 43–46). We have not observed
them in the Synaptera (Lepisma and Machilis).

In the Dermaptera the taste-cups appear to be undeveloped in the
nymph, while in the adult they are fewer in number than in any other
pterygote order yet investigated.

In a species of Forficula from Cordova, Mexico, the taste-pits are
few in number, there being only about a dozen on each side in all;
most of them being situated on the anterior half, and a few near the
base. The taste-pits are provided each with a short fine seta, as
usual arising from the centre.

FIG. 286.—Under side of left maxilla of Vespa: _Gm_, taste-cups;
_Shm_, protecting hairs; _Tb_, tactile hairs; _Mt_, base of
maxillary palpus.—After Will.
]

In the order Platyptera (including Perla, Pteronarcys, Psocus,
Termes, Eutermes, and Termopsis) we have been unable to detect any
organs of taste.

FIG. 287.—Section through a taste-cup: _SK_, supporting cone; _N_,
nerve; _SZ_, sense-cell.—After Will. This and Figs. 284–286 from
Lubbock.
]

FIG. 288.—Tongue of worker honey-bee: _pg_, paraglossæ; _B_, the
same enlarged, showing the taste-papillæ; _C_, _D_, base of a
labial palpus (_mx.′p_) with the taste-papillæ; _E_, taste-cups on
paraglossæ of Bombus; _F_, group of same on left, _G_, on right
side, at base of labial palpus.
]

In the Odonata, however, they are fairly well developed; in
Calopteryx, about 50 taste-cups were discovered; in a species of
Diplax about 28, there being a group of 14 at the base of the
epipharynx on each side of the median line, while in _Æschna heros_
there are two groups of from 25 to 30 taste-cups, situated as in the
two aforenamed genera.

In the Orthoptera the gustatory cups are numerous, well developed,
and present in all the families except the Phasmidæ, where, however,
they may yet be found to occur.

In a large cockroach (Blabera) from Cuba they are well developed. On
each side of the middle of the epipharynx is a curved row of stiff,
defensive spines, and at the distal end of each row is a sensory
field, containing 20 taste-cups on one side and 23 on the other.
Near the front edge of the clypeal region are two more sensory
fields, situated on each side of the median line, there being 35
taste-cups in each field. The taste-cups in this form are rather
smaller than usual in the order.

In the Acrydiidæ they are more numerous than in the Blattidæ. For
example, in _Camnula pellucida_, near what corresponds to the front
edge of the clypeus are two gustatory fields, each bearing about 35
taste-pits. Just in front, under the clypeo-labral suture, are two
similar fields, each containing from 40 to 42 taste-pits. There are
none in front of these. There are thus about 140–150 sense-cups in
all.

The members of the Locustidæ (Fig. 26) appear to be better provided
with the organs of taste than any other Orthoptera, those of the
katydid numbering from 170 to 180. There are from 50 to 60
taste-cups in the front region; behind the middle a group of 25 on
each side, and over an area corresponding to the base of the labrum
and front edge of the clypeus is a sensory field with about 70
taste-cups on each side. They are true cups or beaker-like papillæ,
some with a fine, others with a short, stout, conical seta.

The gustatory organs in the cave cricket (_Hadenœcus subterraneus_,
Fig. 27), from Mammoth Cave, are highly developed, being rounded
papillæ with the nucleus at the top or end. They are grouped on each
side of the middle near the front edge, there being 25 on each side.
An irregular row of these beaker-like organs extends along each
side; some occur under the base of the labrum, but they are most
numerous in a field corresponding to the front edge of the clypeus,
there being 50 on each side, or 100 in all, where in Ceuthophilus
there are only 9 or 10. It would thus appear as if the sense of
taste were much more acute in the cave-dweller than in the
out-of-doors form.

In the Coleoptera taste-cups and setæ are very generally
distributed, though we were unable to detect them in Dendroctonus or
in _Lucanus dama_. As seen in Fig. 57, we have observed numerous
taste-pegs along the maxilla of _Nemognatha lurida_, but otherwise
taste-organs have only been detected in the epipharynx. They not
only occur in the adult beetles, but we have found them in the larvæ
of cerambycid, scarabæid, and other beetles. In the adults
taste-cups appear to be about as well developed in the carnivorous
forms (Carabidæ) as in the phytophagous or lignivorous groups.

In _Chlænius tomentosus_ there are about half as many of these
organs as in Harpalus, while in Calosoma there are 90 taste-cups, 45
on each side, under the base of the labrum. The cups are
papilliform, being rather high, with a seta arising from each.

In the Cicindelidæ, the epipharynx bears a sensory field quite
different from that of the Carabidæ. There are no normal taste-cups,
except a few situated on two large, round, raised areas which are
guarded in front by a few very long setæ. On the surface of each
area are numerous very long setæ which may, if not tactile, have
some other sense, as they arise from cup-like bases or cells. Those
on the outside are like true taste-cups, with a bristle but little
larger than normal in taste-cups generally. We are disposed to
regard this sensory field as a highly specialized gustatory
apparatus.

In the Dyticidæ the taste-cups are nearly as described in the
Carabidæ.

The Staphylinidæ are not well provided with taste-organs. Under the
clypeus of _Staphylinus violaceus_, on each side near the middle, is
a bare rounded area, in which are situated 4 or 5 papilliform
taste-cups, and at the base behind them is another linear group of
about 7 slenderer, somewhat curved, taste-cups. In the Elateridæ
these organs are scantily developed.

In the Buprestidæ (_Buprestis maculiventris_ alone examined) no true
taste-cups were detected. On the other hand, the Lampyridæ are well
supplied with them. Under the clypeus is situated a sensory field
bearing 26 taste-cups, which are rather smaller than usual. Over the
epipharyngeal surface are scattered a few taste-cups, but they are
small and perhaps not gustatory. Under the clypeus of _Lucidota
punctata_ Lec. is a group of 12 taste-cups, and in the middle region
of the epipharynx, situated in a field extending from near the base
to near the front edge, are about 40 taste-cups, which, however, are
not, as is usual, arranged on each side of the median line, but are
scattered among the hairs of the pilose surface of the epipharynx.
In the Cleridæ the taste-cups are few in number.

In the great family of Scarabæidæ, the presence of gustatory organs
is variable. None occur in _Lucanus dama_, though in the June beetle
(_Lachnosterna fusca_ Fröhl.) they are abundantly developed. The
epipharynx bears on each side outside of a spiny area a group of
about 50 taste-cups, each bearing a long seta, those on the outside
of the area passing into a few high, rather slender, papillæ,
without a seta. On the under side of the clypeus is a median group
of 10 taste-cups of singular form, the cups being large, with broad
bases, which posteriorly bear three spines, of which the median one
is the largest.

Taste-cups occur without any known exception in the longicorn
beetles. In _Leptura canadensis_ they are numerous; in _Euryptera
lateralis_ they are abundant along and near the middle of the
anterior half of the labral region, and in _Cyllene robiniæ_ Forst.
(or _pictus_ Drury) they are more numerous than usual, extending in
an unbroken sensory field from near the front margin of the clypeal
region to near the front edge of the epipharynx. The cups vary much
in size, some being one-half as large as others; and those on the
sides of the sensory field bear short, and a few others rather long,
bristles, showing that the taste-cups are modified tactile bristles.

The Tenebrionidæ are fairly well endowed with taste-cups, their
number in _Eleodes obsoleta_ Say amounting to 30 or 40.

Those of the Meloidæ especially are unusual in size and number.

FIG. 289.—Epipharynx (_ep_) of Nemognatha: _cl_, clypeus; _gh_,
gathering hairs; _tc_, triangular sensory field dotted with taste
cups; _A_, the field enlarged.
]

In _Nemognatha lurida_ Lec. (Fig. 289) the front edge of the
epipharynx contains about 80 remarkably small taste-cups, arranged
irregularly in a triangular sensory space, and not more than ¼ to ⅙,
as large as those on the maxillæ of the same beetle. Unless the
former structures are gustatory it is difficult to account for their
presence here, and it will be observed that the taste-cups in
Epicauta are unusually abundant. Thus in the middle and near the
front of the epipharynx of the blister-beetle over 100 gustatory
cups were counted. They are conical, papilliform, and truncated at
the end as if open, the edge of the opening being ragged, though
bearing no bristle, except in a few cases. Around the edge of the
sinus, on the under side of the labrum, is a regular marginal row of
large, longer, more distinctly chitinized taste-cups, whose walls
are streaked up and down by chitinous thickenings. In _E. callosa_
Lec. there are about 55 taste-cups under the labrum, besides about
10 cells, which may be gustatory structures, situated on either side
of a median setose ridge which passes back under the clypeal region.

The taste-cups of the leaf-beetles are fairly numerous, judging from
an examination of _Diabrotica vittata_. The surface of the
epipharynx is pilose, but the median region is naked, and on the
anterior half bears from 11 to 12 taste-cups, arranged each side of
the median line in a rude Y. On each side, at the base of the labial
region, are two sensitive fields, each bearing about 25 to 26
taste-cups. More were seen under the clypeus.

In the Neuroptera unmistakable taste-cups are not always present. In
_Sialis infumata_ along the median line of the epipharynx and near
the front are about 20 scattered gustatory pegs, which are minute,
but longer and more acute than usual. In _Chauliodes maculatus_
there are one or two taste-cups under the front edge of the clypeus;
others are scattered along the middle from the base of the labrum to
the front, but are not arranged in definite order. In _Corydalis
cornutus_ no sense-cups, pits, or rods are present. In Chrysopa
there are scattered cups armed with a short acute bristle, which are
possibly gustatory in function. In _Myrmeleon diversum_ also the
presence of sense-pits or of taste-cups is doubtful, though a group
of about 12 pits on each side of the clypeal region of the
epipharynx, and a few situated at the base of the labral region, may
be endowed with the sense of taste. In _Mantispa brunnea_, however,
along the middle of the epipharynx are scattered about 30
unmistakable taste-cups, each bearing a short, fine hair.

In the Mecoptera (_Panorpa debilis?_) taste-cups, giving rise to a
minute hair, occur on the labium in two regions, and also on the
maxillæ situated on the stipes near the base of the palpi, and on
the lacinia and galea. They are also to be found on the maxillæ of
_Boreus californicus_, but were not detected on the labium.

They were first detected by Reuter in various microlepidoptera, and
occur on the “basal spot” of the palpi of many butterflies. In a
Tineid moth (_Coleophora coruscipennella_) we have detected what we
suppose to be a group of four taste-pits on the inner side of the
basal joint of the labial palpi.

=Experimental proof.=—No one, says Lubbock, who has ever watched a bee or wasp can entertain the slightest doubt as to their possession of the sense of taste. “Forel mixed morphine and strychnine with some honey, which he offered to his ants. Their antennæ gave them no warning. The smell of the honey attracted them, and they began to feed; but the moment the honey touched their lips they perceived the fraud.”

Will at first fed wasps with sugar, so that they frequently visited it; afterwards he substituted alum for the sugar. Eagerly flying to it, they had scarcely touched it when they drew back from the distasteful substance with the most comical gestures, and cleaned their tongues by frequently running them in and out, repeatedly stroking them with their fore feet. He noticed a great repugnance to quinine in nearly all the insects experimented on. Bees and wasps were observed to have a more delicate gustatory sense than flies, etc., which are more omnivorous in their tastes.

LITERATURE ON THE ORGANS OF TASTE

=Meinert, F.= Bidrag til de danske myrers naturhistorie. (Kgl. Dansk
Vidensk. selsk. skrifter. Kjoebenhavn. Raekke 5 Naturvid. og math.
Afd., v, 1861, pp. 273–340.)

=Wolff, O. J. B.= Das Riechorgan der Biene. (Nova acta d. K.
Leop.-Carol. Akad., xxxviii, 1875, pp. 1–251, 8 Taf.)

=Joseph, G.= Zur Morphologie des Geschmacksorganes bei Insekten.
(Amtlicher Bericht der 50. Versammlung deutscher Naturforscher und
Aerzte in München, 1877, pp. 227–228.)

=Künckel et Gazagnaire.= Du siège de la gustation chez les insectes
Diptères. Constitution anatomique et physiologique de l’epipharynx
et l’hypopharynx. (Comptes-rend. Acad. Sc., Paris, 1881, xcv, pp.
347–350.)

—— Recherches sur l’organisation et le développement des Diptères et
en particulaire des Volucelles, i, 1875, ii, 1881, 26 Pls.

=Kraepelin, K.= Zur Kenntniss der Anatomie und Physiologie des Rüssels
von Musca. (Zeitschr. f. wissens. Zool., xxxix, 1883, pp. 683–719, 2
Taf.)

=Kirbach, P.= Ueber die Mundwerkzeuge der Schmetterlinge. (Zool.
Anzeiger, 1883, pp. 553–558, 2 Figs.)

=Will, F.= Das Geschmacksorgan der Insekten. (Zeitschr. f. wissens.
Zool., 1885, xlii, pp. 674–707, 1 Taf.)

=Gazagnaire, J.= Du siège de la gustation chez les insectes
Coléoptères. (Comptes-rend. Acad. Sc., Paris, 1886, cii, pp.
629–632; Ann. Soc. Ent. France, Sér. 6, Bull., pp. 79–80.)

=Forel, A.= Expériences et remarques critiques sur les sensations des
insectes. 2^{me} Part. (Recueil Zool. Suisse, iv, 1887, pp.
161–240.)

=Reuter, Enzio.= Ueber den “Basalfleck” auf den Palpen der
Schmetterlinge. (Zool. Anzeiger, 1888, pp. 500–503.)

—— Ueber die Palpen der Rhopaloceren, etc., 6 Taf. Helsingfors, 1896,
pp. 1–578. (Acta Soc. Sc. Fennicæ, xxii, 1896.)

=Packard, A. S.= On the occurrence of organs, probably of taste, in
the epipharynx of the Mecoptera (Panorpa and Boreus). (Psyche, 1889,
v, pp. 159–164.)

—— Notes on the epipharynx, and the epipharyngeal organs of taste in
mandibulate insects. (Psyche, 1889, v, pp. 193–199, 222–228.)

Also Lubbock’s Senses, etc., of animals, and the writings of Briant,
Breithaupt (titles on p. 85).

_d._ The organs of hearing

Although it has been denied by Forel that insects have the sense of hearing, yet the majority of writers and experimenters agree that insects are not deaf. On general grounds if, as we know, many insects produce sounds, it must follow that they have ears to hear, for there is every reason to suppose that the sounds thus made are, as in other animals, either for attracting the sexes, for a means of communication, or to express the emotions. We will begin by briefly describing the structures now generally supposed to be auditory in function, and about which there can be no reasonable doubt, and then consider the more problematical organs, closing with an account of the extremely various means of producing sounds and cries.

=The ears or tympanal and chordotonal sense-organs of Orthoptera and other insects.=—The ears or tympana of locusts (Acrydiidæ) are situated one on each side, on the basal joint of the abdomen, just behind the first abdominal spiracle. That this is a true ear was first suggested by J. Müller, and his opinion was confirmed by Siebold, Leydig, Hensen, Graber, Schmidt, Lubbock, etc.[49]

FIG. 290.—Ear of a locust (_Caloptenus italicus_), seen from the inner
side: _T_, tympanum; _TR_, its border; _o_, _u_, two horn-like
processes; _bi_, pear-shaped vesicle; _n_, auditory nerve; _ga_,
terminal ganglion; _st_, stigma; _m_, opening, and _m′_, closing,
muscle of the same; _M_, tensor muscle of the tympanum
membrane.—After Graber.
]

The apparatus consists of a tense membrane, the _tympanum_, surrounded by a horny ring (Fig. 290). “On the internal surface of this membrane are two horn-like processes (_o_, _u_), to which is attached an extremely delicate vesicle (_bi_) filled with a transparent fluid, and representing a membranous labyrinth. This vesicle is in connection with an auditory nerve (_n_) which arises from the third thoracic ganglion, forms a ganglion (_ga_) upon the tympanum, and terminates in the immediate neighborhood of the labyrinth by a collection of cuneiform, staff-like bodies, with very finely pointed extremities (primitive nerve-fibres?), which are surrounded by loosely aggregated ganglionic globules” (Siebold’s Anatomy of the Invertebrates).

FIG. 291.—Fore tibia of _Locusta viridissima_. _td_, cover of the
drum; _tr_, fissure between the drum and its cover.—After Graber,
from Lang.
]

In the green grasshoppers, katydids, and their allies, the ears are situated on the fore tibiæ, where these organs can be found after a careful search (Figs. 291, 292).

The presence of the structure is indicated by the oval disc, the drum, which is a thin tense membrane covering the auditory apparatus of nerves, ganglion cells, and auditory rods beneath.

The tympana, or drums, are not present in all Locustidæ and
Gryllidæ, and, as Lubbock states, it is an additional reason for
regarding them as auditory organs, that in those species which
possess no stridulating organs the tympana are also wanting. In many
of the Locustidæ the tympana are covered or protected by a fold of
the skin projecting over them. These covered ones are, Graber
thinks, derived from the open ones.

FIG. 292.—_A_, fore tibia of a European grasshopper (Meconema),
containing the ear: _Ty_, tympanum or outer membrane; _Tr_ 1, _Tr_
2, tracheæ. _B_, diagrammatic cross-section through the tibia and
ear of the same; _Ty_, tympanum; _Ct_, cuticula; _CM_, hypodermis:
_A_, the auditory organ connecting with the tympanum; _B_,
supra-tympanal auditory organ; _GZ_, the ganglion-cell belonging
to them; _Hst_, the auditory rod connecting with the
ganglion-cells.—After Graber, from Judeich and Nitsche.
]

On examining the apparatus within the leg under the drum, it is seen to consist of the trachea, the auditory vesicles and rods, ganglion cells, and acoustic nerve. The trachea is greatly modified (Fig. 292, _Tr_ 1). On passing into the tibia the trachea enlarges and divides into two branches, which reunite lower down. The spiracles supplying the air to this enlarged trachea are considerably enlarged, while in the dumb species it is of the normal size. The enlarged trachea passes close to the tympanum, which thus has air on both sides of it: the open air on the outer, the air of the trachea on its inner surface. In fact, as Lubbock states, “the trachea acts like the Eustachian tube in our own ear; it maintains an equilibrium of pressure on each side of the tympanum, and enables it freely to transmit the atmospheric vibrations.”

FIG. 293.—The auditory apparatus in the tibia of a grasshopper,
showing the tympanal nerve-endings in situ: _EBI_, terminal vesicles
of Siebold’s organ; _SN_, nerve of the organ of Siebold; _Gr_, group
of vesicles of same; _SO_, nerve-endings of the same; _vT_, front
tympanum; _vTr_, front branch of the trachea; _hT_, hinder tympanum;
_hTr_, hinder branch of the trachea; _Sp_, space between the
tracheæ; _go_, supra tympanal ganglion; _rN_, connecting
nerve-fibrils between the ganglion cells and the terminal vesicles;
_R_, upper, _n-S_, lower, root of the transparent covering membrane.
(Other lettering not explained by author.)—After Graber.
]

FIG. 294.—Auditory rod of _Gryllus viridissimus_: _fd_, auditory rod;
_ko_, terminal piece.—After Graber, from Lubbock.
]

These tracheæ, says Graber, though formed on a similar plan, present
many variations, corresponding to those of the tympana, and showing
that the tympana and the tracheæ stand in intimate connection with
one another. For instance, in those species where the tympana are
equal, the tracheæ are so likewise; in Gryllotalpa, where the front
tympanum only is developed, though both tracheal branches are
present, the front one is much larger than the other; and where
there is no tympanum, the trachea remains comparatively small, and
even in some cases undivided (Lubbock, _ex_ Graber).

The acoustic nerve, which next to the optic is the thickest in the body, divides soon after entering the tibia into two branches, one almost immediately forming a ganglion, the supra-tympanal ganglion, the other passing down to the tympanum, where it expands into an elongated flat ganglion, the organ of Siebold (Fig. 293), and closely applied to the anterior tracheæ.

At the upper part of the ganglion is a group terminating below in a single row of vesicles, the first few of which are approximately equal, but which subsequently diminish regularly in size. Each of these vesicles is connected with the nerve by a fibril (Fig. 293, _vN_), and contains an auditory rod (Fig. 294). They are said by Graber to be brightly refractive, hollow (thus differing from the retinal rods, which are solid), and terminate in a separate end-piece (_ko_). The rods were first discovered by Siebold, and, as Lubbock remarks, may be regarded as specially characteristic of the acoustic organs of insects.

FIG. 295.—Chordotonal organ in nymph of a white ant.—After Müller,
from Sharp.
]

FIG. 296.—Right half of 8th body-segment of _Corethra plumicornis_:
_g_, ganglion of ventral cord; _lm_, longitudinal muscle; _cn_,
chordotonal nerve; _cl_, chordotonal ligament; _cg_, chordotonal
ganglion; _cs_, rod of chordotonal organ; _cst_, terminal cord;
_tb_, tactile setæ; _hn_, out-going fibres of the integumental
nerves.—After Graber, from Lang.
]

As will be seen in Fig. 293, at the upper part of the tibial organ
of Ephippigera there is a group of cells, and below them a single
row of cells gradually diminishing in size from above downwards.
“One cannot but ask oneself,” says Lubbock, “whether the gradually
diminishing size of the cells in the organ of Siebold may not have
reference to the perception of different notes, as is the case with
the series of diminishing arches in the organ of Corti of our own
ears.”

These organs were supposed to be restricted to the Orthoptera, but
in 1877 Lubbock discovered what seems to resemble the supra-tympanal
auditory organ of Orthoptera in the tibia of the yellow ant (_Lasius
flavus_). Graber confirmed Lubbock’s account, and also discovered
these organs in the tibia of a Perlid (_Isopteryx apicalis_), and
Fritz Müller has detected them in the fore tibiæ of the nymph of
_Calotermes rugosus_ (Fig. 295). To these structures Graber gave the
name of chordotonal organs.

He has also detected these organs in all the legs of other insects
(Trichoptera, Pediculidæ), and auditory rods have been discovered in
the antennæ of Dyticus and of Telephorus by Hicks, Leydig, and
Graber. Graber classifies the chordotonal organs into truncal and
membral. In Coleoptera and Trichoptera they may occur on several
joints of the leg; others are more localized,—thus he distinguishes
femoral (Pediculidæ), tibial (Orthoptera, Perlidæ, Formicidæ), and
tarsal organs (Coleoptera).

A type of chordotonal organ, observed in the body-segments of the
larvæ of several insects by Leydig, Weismann, Graber, Grobben, and
Bolles Lee, is to be seen in the transparent larva of Corethra (Fig.
296), where the auditory organ extends to the skin. It contains at
the point _cs_ two or three auditory rods. In the opposite direction
a fine ligament (_cl_) passes from _cg_ to the skin; in this way the
auditory organ is suspended in a certain state of tension, and is
favorably situated to receive even very fine vibrations. A similar
apparatus has been detected in the larva of Ptychoptera.

=Antennal auditory hairs.=—It is not at all improbable that the antennæ of different insects contain auditory as well as olfactory structures. Lubbock has suggested that the singular organs which have only been found in the antennæ of ants and certain bees, and to which he gives the name of “Hicks’ bottles” (Fig. 281), may act as microscopic stethoscopes, while Leydig also regards them as chordotonal organs.

That, however, some of the antennal hairs of the mosquito, as first suggested by Johnson and afterwards proved experimentally by Mayer, are auditory, seems well established. Fastening a male mosquito down on a glass slide, Mayer then sounded a series of tuning-forks. With an Ut_{4} fork of 512 vibrations per second, some of the hairs were seen to vibrate vigorously, while others remained comparatively at rest. The lower (Ut_{3}) and higher (Ut_{5}) harmonics of Ut_{4} also caused more vibration than any intermediate notes. These hairs, then, are specially tuned so as to respond to vibrations numbering 512 per second. Other hairs vibrated to other notes, extending through the middle and next higher octave of the piano.

Mayer then made large wooden models of these hairs, the one corresponding to the Ut_{3} hair being about a metre in length, and on counting the number of vibrations they made when they were clamped at one end and then drawn on one side, he found that it “coincided with the ratio existing between the numbers of vibrations of the forks to which covibrated the fibrils,” or hairs. It should be observed that the song of the female mosquito corresponds nearly to this note, and would consequently set the hairs in vibration. Mayer observed that the song of the female vibrates the hairs of one of the antennæ more forcibly than those of the other. Those auditory hairs are most affected which are at right angles to the direction from which the sound comes. Hence from the position of the antennæ and the hairs a sound will be loudest or most intense if it is directly in front of the head. If, then, the song of the female affects one antenna more than another, the male turns his head until the two antennæ are equally affected, and is thus able to fly straight towards the female. From his experiments Mayer found that the male can thus guide himself to within 5° of the direction of the female. Hence he concludes that “these insects must have the faculty of the perception of the direction of sound more highly developed than in any other class of animals.” (Also see Child’s work.)

=Special sense-organs in the wings and halteres.=—Organs of a
special sense, which Hicks supposed to be those of smell, were found
by him near or at the base of the wings of Diptera, Coleoptera, and
less perfect ones in Lepidoptera, Neuroptera, and Orthoptera, with a
trace of them in Hemiptera; but these were considered by Leydig to
be auditory organs, since he found the nerves to end in club-shaped
rods, like those of Orthoptera.

Hicks found, as to the halteres and their sense-organs, that the
nerve in the halter is the largest in the insect, except the optic
nerve; and that at the base of the halteres is a number of vesicles
arranged in four groups, to each of which the nerve sends a branch.
Afterwards Bolles Lee discovered that the vesicles, undoubtedly
perforated, contain a minute hair, those of the upper groups being
protected by hoods of chitin. He regarded them as olfactory organs,
while Lubbock seems inclined to consider them as auditory
structures. Graber also regards the vesicles of Hicks as chordotonal
organs.

In his elaborate account of the balancers, Weinland concludes that
the organs of sense of varying structure occurring at the base of
these appendages allow the perception of movements which the
halteres perform and which enable the fly to steer or direct its
course. The halteres can thus cause differences in the direction of
the flight of a fly in the vertical plane. If the balancers act
unequally, there is a change in direction.

_e._ The sounds of insects

Insects have no true voice; but sounds of different intensity, shrill cries, and other noises are produced mechanically by insects, either being love-songs to attract the sexes, to give signals, to communicate intelligence, or perhaps to express the emotions. The loud, shrill cry of the Cicada, or chirp of the cricket, is evidently a love-call, and results in the mating of individuals of separate broods more or less widely scattered, thus preventing too close interbreeding.

The simplest means of making a noise is that of the death-watch (Anobium), which strikes or taps on the wall with its head or abdomen. Longicorn beetles make a sharp sound by the friction of the mesoscutellum against the edge of the prothoracic cavity, the head being alternately raised and lowered, Burying-beetles (Necrophorus) rub the abdomen against the hinder edges of the elytra. Weevils make a loud noise by rapidly rubbing the tips of the abdomen on the ends of the elytra.

Landois offers the following summary of the kinds of noises produced
by beetles:

1. Tapping sounds (Bostrycinæ, Anobium).

2. Grating sounds (Elateridæ).

3. Friction without special rasping organs (_Euchirus
longimanus_).

4. Rasping sounds produced by friction:

_a._ Rubbing of the pronotum on the mesonotum (Cerambycidæ
except Spondyli and Prionus).

_b._ Friction of the prosternum on the mesosternum (_Omaloplia
brunnea_).

_c._ Elytra with a rasp at the end (Curculionidæ, Dyticidæ,
Pelobius).

_d._ With a coxal rasp (Geotrupes, Ceratophyus). The male of
Ateuchus stridulates to encourage the female in her work, and
from distress when she is removed. (Darwin.)

_e._ Friction of the edge of the elytra against the femur
(_Chiasognathus grantii_).

_f._ Pygidium with two rasps in the middle (Crioceris, Lema,
Copris, Oryctes, Necrophorus, Tenebrionidæ).

_g._ Abdomen with a grating ridge and four grating plates
(Trox).

_h._ Abdomen with two toothed ridges rubbing on a rasp on edge
of wing-cover (Elaphus, Blethisa, Cychrus).

_i._ Rubbing the elytra on a rasp on the hind wings (_Pelobius
hermanni_).

_j._ Friction of the wing against the abdominal segments
(_Melolontha fullo_).

Mutilla makes a rather sharp noise by rubbing one abdominal segment
against another. Ants (Ponera) have a stridulating apparatus, and
other genera numerous (20) ridges between the segments.

Even certain moths and butterflies emit a rasping or crackling
noise. The death’s-head moth and other sphinges cause it by rubbing
the palpi against the base of the proboscis. These and certain
butterflies are provided with parallel ridges forming a rasp on the
“basal spot” of the inner side of the basal joint of each palpus
(Reuter). A South American butterfly (_Ageronia feronia_) can be
heard for several yards as it flies with a crackling sound. Hampson
finds that the cause of the clicking sound is due to a pair of
strong chitinous hooks attached to the thorax, against which play
the spatulate ends of a pair of hooks attached to the fore wings. An
Australian moth (Hecatesia) flies with a whizzing sound; Vanessa is
said to be sonorous.

The males of Orthoptera produce their shrill cries or chirping
noises, 1, by rubbing the thighs against the sides of the body
(Acrydiidæ); 2, by the friction of the base of the fore wings on
each other (Locustidæ); 3, by rubbing the base of the upper on the
base of the hinder or under pair (Gryllidæ), in the two last there
being a shrilling apparatus consisting of a file on the hind wings,
which rubs on a resonant surface on the fore wings. The females are
not invariably dumb, both sexes of the European Ephippigera being
able to faintly stridulate. Corixa also produces shrill chirping
notes. (Carpenter.)

Certain insects also hum, and have what may perhaps be called a voice. The cockchafer, besides humming with the wings, produces a sound almost like a voice. In the large trachea, just behind each spiracle, is a chitinous process, which is thrown into vibrations by the air during respiration, and thus produces a humming noise. (Lubbock.) Such is also the case with flies, the mosquito, dragon-flies, and bees. In flies and dragon-flies the “voice” is caused by the air issuing from the thoracic spiracles; while in the humble-bee the abdominal spiracles are also musical. The sound made by the spiracles bears no relation to that caused by the wings. Landois tells us that the wing-tone of the honey-bee is A′; its voice, however, is an octave higher, and often goes to B″ and C″.

The sounds produced by the wings are constant in each species, except where, as in Bombus, there are individuals of different sizes; in these the larger ones generally give a higher note. Thus the comparatively small male of _Bombus terrestris_ hums on A′, while the large female hums an entire octave higher.

From the note produced the rapidity of the vibrations can be calculated. For example, the house-fly, which produces the sound of F, vibrates its wings 21,120 times in a minute, or 335 times in a second; and the bee, which makes a sound of A′, as many as 26,400 times, or 440 times in a second. On the contrary, a tired bee hums on E′, and therefore, according to theory, vibrates its wings only 330 times in a second. Marey has confirmed these numbers graphically, and found by experiment that the fly actually makes 330 strokes in a second. (Lubbock.)

A different kind of musical apparatus is that of the cicada, which has been elaborately described by Graber. The shrill, piercing notes issue from a pair of organs on the under side of the base of the abdomen of the male, these acting somewhat as two kettle-drums, the membrane covering the depressions being rapidly vibrated.

LITERATURE ON THE ORGANS OF HEARING

_a._ The auditory organs

=Siebold, C. Th. E. von.= Ueber das Stimm- und Gehörorgan der
Orthopteren. (Archiv f. Naturgesch., 1844, x, pp. 52–81.)

=Johnston, Christopher.= Auditory apparatus of the culex mosquito.
(Quart. Journ. Micr. Soc., 1855, iii, pp. 97–102, 1 Fig.)

=Hicks, Braxton.= On a new organ in insects. (Journ. Linn. Soc. Zool.,
London, 1857, pp. 130–140, 1 Pl.)

—— Further remarks on the organ found on the bases of the halteres and
wings of insects. (Trans. Linn. Soc., London, 1857, xxii, pp.
141–145, 2 Pls.)

=Hensen, V.= Ueber das Gehörorgan von Locusta. (Zeitschr. f. wissens.
Zool., xvi, 1866, pp. 190–207.)

=Graber, V.= Bemerkungen über die Gehör- und Stimmorgane der
Heuschrecken und Cicaden (Wiener Sitzungsber. Math.-natur-wiss. Cl.,
lxvi, 1 Abt., 1872, pp. 205–213, 2 Figs.)

—— Die tympanalen Sinnesapparate, der Orthopteren. (Denkschr. d. k.
Akad. d. wissens. Wien, xxxvi, 1876, 2 Abt., pp. 1–140, 10 Taf.)

—— Die abdominalen Tympanalorgane der Cicaden und Gryllodeen. (Ibid.,
1870, xxxvi, pp. 273–290, 2 Taf.)

—— Ueber neue, otocystenartige Sinnesorgane der Insekten. (Archiv f.
mikroskop. Anat., 1878, pp. 35–57, 2 Taf.)

—— Die chordotonalen Sinnesorgane und das Gehör der Insekten. (Archiv
f. mikroskop. Anat., 1882, xx, pp. 506–640; 1883, xxi, pp. 65–145,
Taf.)

=Mayer, Alfred Marshall.= Researches in Acoustics No. 5. 3.
Experiments on the supposed auditory apparatus of the culex
mosquito. (Amer. Jour. Sc. and Arts, Ser. 3, viii, 1874, pp. 81–103;
also Amer. Naturalist, viii, pp. 577–592.)

=Schmidt, Oscar.= Die Gehörorgane der Heuschrecken. (Archiv f.
mikroskop. Anat., xi, 1875, pp. 195–215, 3 Taf.)

=Ranke, J.= Beiträge zu der Lehre von den Uebergangssinnesorganen, das
Gehörorgan der Acridier und das Sehorgan der Hirudineen. (Zeitschr.
f. wissens. Zool., xxv, 1875, pp. 143–164, 1 Taf.)

=Lee, A. Bolles.= Les balanciers des Diptères, leurs organes
sensifères et leur histologie. (Recueil Zool. Suisse, ii, 1885, pp.
363–392, 1 Pl.)

—— Bemerkungen über der feineren Bau der Chordotonalorgane. (Archiv f.
mikroskop. Anat., 1883, xxiii, pp. 133–140, 1 Taf.)

—— Les organes chordotonaux des Diptères et la méthode du chlorure
d’or. (Observations critiques.) (Recueil Zool. Suisse, 1884, ii, pp.
685–689, 1 Pl.)

=Weinland, E.= Ueber die Schwinger (Halteren) der Dipteren (Zeitschr.
f. wissens. Zool., 1890, li, pp. 55–166, 5 Taf.)

=Adelung, N. v.= Beiträge zur Kenntnis des tibialen Gehörapparates der
Locustiden. Inaug. Diss., Leipzig, 1892, 2 Taf.

=Child, Ch. M.= Ein bisher wenig beachtetes antennales Sinnesorgan der
Insekten, mit besonderer Berücksichtigung der Culiciden und
Chironomiden. (Zeitschr. f. wissens. Zool., lviii, 1894, pp.
475–528, 2 Taf.; also, Zool. Anzeiger, xvii Jahrg., pp. 35–38, and
in Annals and Mag. Nat. Hist., 1894 (6), xiii, pp. 372–374).

Also the writings of J. Müller, Kirby and Spence, Burmeister, Gilbert
White, Westwood, Guilding, Meinert, Paasch, Leydig, Viallanes,
Minot, Forel, Mayer, Darwin (Descent of Man, i, ch. x.), F. Müller,
Lubbock (Senses of animals), Westring, Köppen, Bates, Vom Rath,
Peckham, Jourdan, Nagel, etc.

_b._ The sounds made by insects

=Scudder, S. H.= Notes on the stridulation of grasshoppers. (Proc.
Bost. Soc. Nat. Hist., xi, 1868, pp. 306–313 and 316.)

—— The songs of the grasshoppers. (Amer. Naturalist, ii, 1868, pp.
113–120, 5 Figs.)

=Riley, C. V.= The song notes of the periodical Cicada. (Proc. Amer.
Assoc. Adv. Science, xxxiv, 1885, pp. 330–332; also in Kansas City
Rev., October, 1885, pp. 173–175.)

=Swinton, A. H.= (Ent. Month. Mag., 1877.) Sound produced in Ageronia
by a modification of the hook and bristle of the wings.

=Hampson, G. F.= On stridulation in certain Lepidoptera, etc. (Proc.
Zool. Soc. London, 1892, ii, pp. 188–193, Fig; also Psyche, vi, p.
491, 1 Fig.)

With the writings of Landois, Lubbock, Graber, Kolbe, Carpenter (Nat.
Science), Bruyant, and others.

THE DIGESTIVE CANAL AND ITS APPENDAGES