$ 336. THE INSECTA. 417 
fore-legs directly below the coxo-tibial articulation.” With a part of the 
Losustidae,“ there is, on each side at this point, a fossa; while with 
another portion of this family, there are, at this same place, two more or 
less spacious cavities (Auditive capsules) provided with orifices opening 
forwards. These fossae and these cavities have each on their internal 
surface, a long-oval tympanum. The principal trachean trunk of the leg 
passes between the two tympanums, and dilates, at this point, into a vesicle 
whose upper extremity is in connection with a ganglion of the auditory 
nerve. This last arises from the first thoracic ganglion, and accompanies. 
the principal nerve of the leg. From this ganglion in question passes off a 
hand of nervous substance which stretches along the slightly excavated 
anterior side of the trachean vesicle. Upon this band is situated a row 
of transparent vesicles containing the same kind of cuneiform, staff-like 
bodies, mentioned as occurring with the Acrididae. ‘The two large tra- 
chean trunks of the fore-legs open by two wide, infundibuliform orifices on 
the posterior border of the prothorax, so that here, as with the Acrididae, 
a part of this trachean apparatus may be compared to a Tuba Eustachii.™ 
With the Achetidae, there is on the external side of the tibia of the fore- 
legs, an orifice closed by a white, silvery membrane (Tympanum), behind 
which is an auditory organ like that just described. 
§ 336. 
The organs of Vision consist of simple, or of compound eyes.” The 
first occur chiefly with the larvae of holometabolic Insecta; and the second 
with Insecta in their perfect state. There are, however, many species 
which have both kinds of eyes in their imago state. These organs are 
_ wanting with only a few adult Insecta,” but are wholly absent with many 
larvae and pupae of the holometabolic species. ® 
1. The Simple eyes (Ocelli, Stemmata) are composed of a convex, 
spheroidal, or elliptical cornea, behind which is situated a spherical or 
cylindrical lens, lodged in a kind of calyx formed by an expansion of the 
optic nerve, and which is surrounded by a variously colored pigment-layer, 
as by a Chorioidea, 
8 See my researches in Wiegmann’s Arch. loc. 
cit. p. 72, Taf. I. fig. 8-17. 
4 Meconema, Barbitistes, Phaneroptera, Phyl- 
loptera. 
5 Decticus, Locusta, Xiphidium, Ephippi- 
gera, Saga, Conocephalus, Callinemus, Acan- 
thodis, Pseudophylius, &c. 
6 In his classification of the Locustidae, Bur- 
meister (Handb. &c. II. p. 673) has made use of 
the different forms of these orifices ; — differences, 
however, which had before been pointed out by De- 
geer (Abhandl. Th. ITI. p. 285, Taf. XX XVII. fig. 
5 and 6) Lansdown Guilding (Linn. Trans. XV. 
1827, p. 153). 
7 These two infundibuliform orifices of the tra- 
cheae, which L. Dufour (Recherch. sur les Orthopt. 
&c. p. 279, Pl. I. fig. 2) has called vessies aérosta- 
tiques, have generally been regarded as the stig- 
mata of the prothorax, although the true stigmata, 
of the ordinary form and size, are situated in front 
of the orifices in question. 
8 With Acheta achatina and italica, there is 
a tympanum of the same size, on the internal sur- 
face of the legs in question ; but it is scarcely ob- 
servable with Acheta sylvestris, domestica and 
campestris ‘ 
These stemmata are sometimes so closely situated 
1 For the eyes of the Insecta, see Marcel de 
Serres, Mem. sur les yeux comp. et les yeux lisses 
d. Ins.; Treviranus, Verm. Schrift. I1I. p. 147, - 
and Beit. zur Anat. u. Physiol. d. Sinneswerkz. 
Hft. I. p. 843 finally, J. Muller, Zur vergleich. 
Physiol. des Gesichtssinn, p. 326, or in Ann. d. Sc. 
Nat. XVII. 1829, p. 242 (in extract), and his Me- 
moir in Meckel’s Arch. 1829, p. 38. ° 
2 The eyes are wanting in many species of Ptili- 
um which live under the bark of trees (Erichson, 
Naturgesch. d. Insekt. Deutschl. III. » 32); with 
Anophthalmus, which live in caverns (Sturm, 
Deutschl. Fauna Abth. V. Bd. XV.), and with Cla- 
viger, which live in ant-nests. 
8 As such may be cited the larvae of Hymeno- 
ptera, excepting, however, those of the Tenthredini- 
dae ; those of the Diptera, which live in decompos- 
ing animal and vegetable substances ; those of the: 
Elateridae, Histeridae, Lamellicornes, Tenebrioni- 
dae, and in general the apodal larvae of Coleo~ 
ptera; finally, the parasitic larvae of the Strepsi- 
ptera, whose females are also blind in the imago 
state, 
4 For the simple eyes of Dytiscus, see Miller, 
in Meckel’s Arch. loc. cit. p. 39, Taf. ITI. fig. 1, 2 5, 
for those of Cicada, Vespa, Bombus, and Libel- 
