<§. 336. THE INSECTA. 41 T 



fore-legs directly below the coxo-tibial articulation.*''* With a part of th& 

 Lo'',ustidae/** 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 cpiestion passes off a 

 band 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 Aehetidae, 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. <'*> 



§ 



ÖOl 



The organs of Vision consist of simple, or of compound eyes.'^^ The 

 first occur chiefly with the larvae of holonietabolic 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.*^' These stemmata are sometimes so closely situated 



3 See my researches in Wie^mann^s Arch. loc. 1 For the eyes of the Insecta, see Marcel de 



cit. p. 72, Taf. I. flg. 8-17. . Serres, Mem, sur les yeux comp, et les yeux lisse» 



* Meconema,Barbitistes,Pkaneroptera,Phyl- d. Ins.; Trevi ranu s, Yerm. Schrift. HI. p. 147, 



loptera. and Beit, zur Anat- u, Physiol, d. Sinneswerltz. 



5 Decticus, Locusta, Xiphidium, Ephippi- Hft. I. p. 84 ; finally, J. Müller, Zur vergleich. 

 ffera, Sai^a, Conocephalus, CaUinemus, Acan- Physiol, des Gesichtssinn, p. 326, or in Ann. A. Sc. 

 thodis, Pseudophyllus, &c. Nat. XVII. 1829, p. 242 (in extract), and his Ale- 



6 In his classification of the Locustidae, Bur- moir in Meckel's Arch. 1829, p. 38. 



meister (Ilandb. &c. II. p. 673) has made use of ^ The eyes are wanting in many species of Pti li- 

 the different forms of these orifices ; — differences, um which live under the baric of trees (Erichso7\ 

 however, which had before been pointed out by De- Naturgesch. d. Insekt. Deutschi. III. p 32) ; with 

 ^ecr (Abhandl. Th. III. p. 285, Taf. XXXVII. fig. Jnophthahnus, which live in caverns (Sturm, 

 5 and 6) Lansdown Guilding (Linn. Trans. XV. Deutschl. Fauna Abth. V. Bd. XV.), and with Cla- 

 1827, p. 153). viger, which live in ant-nests. 



7 These two infundibuliform orifices of the tra^ 3 As such may be cited the larvao of Hymeno- 

 cheae, which L. Dufour (Recherch. sur les Orthopt. ptera, excepting, however, those of the Tenthredini- 

 &c. p. 279, PI. I. fig. 2) has called vessies airosta- dae ; those of the Diptera, which live in decompos- 

 tiques, have generally been regarded as the stig- ing animal and vegetable substances ; those of the 

 mata of the prothorax, although the true stigmata, Elateridae, Histeridae, Lamellicornes, Tenebrioni- 

 of the ordinary form and size, are situated in front dae, and in general the apodal larvae of Ooleo- 

 of the orifices in question. ptera ; finally, the parasitic larvae of the Strepsi- 



8 With Acheta achatina and italica, there is ptera, whose females are also blind in the imago 

 a tympanum of the same size, on the internal sur- state. 



face of the legs in question ; but it is scarcely ob- 4 For the simple eyes of Dytisniis, see Müller, 

 servable with Acheta sylvestris, domestica and in MeckeVs Arch. loc. cit. p. 39, Taf. III. fig. 1, 2 ; 

 campestris for those of Cicada, Vespa, Bombus, and Libel- 



