412 



THE INSECTA. 



^331. 



not yet been definitely fixed. '"'^ The first type consists of an absence of 

 all the longitudinal commissures, as is the case with most of the Ijamelli- 

 cornes, the Curculionidae, and the Scolytidae. Here, the ventral cord is 

 limited to three ganglia connected together ; of these, the first corresponds 

 to the prothorucic, and the second, the larger, to the second and third 

 thoracic ganglia. This last is succeeded by an oblong, ganglionic mass, 

 representing the concentrated abdominal portion of the cord, and from 

 which arise the nerves of the muscles of the abdomen.*''-" In the second 

 typo, the abdominal portion of the cord occupies the entire length of the 

 body. This is the case with the Cistelidae, Oedemeridae and Cerambyci- 

 dae, which have five ganglia in the abdomen.*'-'"' With the larvae of the 

 Coleoptera, these two types are more clearly defined, there being no inter- 

 mediate forms. *-^' 



^ 331. 



The Splanchnic nervous system consists, with the Insecta, in all their 

 states, of a single and a double nervous cord. Sometimes the first, some- 

 times the second of these is the more developed. 



The single Storaato-gastric nerve arises from the anterior border of the 

 cerebral hemispheres, by two short filaments, which, directly in front 

 of the brain, meet in a ganglion (Ganglion frontale) lying upon the oesoph- 

 agus. From this ganglion are given oif several nervous filaments which 

 go to the upper lip ; while, from the opposite side, arises a simple nerve 



18 There lias recently appeared a very detailed 

 memoir, accompanied with beautiful figures, on the 

 nervous system of the Coleoptera, by Blanchard ; 

 see Ann. d. Sc. Nat. V. 1846, p. 273, Pl.VIII.-XV., 

 and Kegne animal, illustr. Insectes, PI. HI. III. 

 bis. and IV. (Me/olontha, Caralius, Otiorhyn- 

 chus, Cerambyx). 



in See Straus, Consider. &c. p. .391, PI. IX. fig. 

 1 (Melolontha vu/garin), and Blanchard, loc. cit. 

 An analogous concentration of the nervous system 

 occurs in the families of Ilisteridae, Gyrinidae, 

 Nitidulidae, and Scaphididae,\vhere the ventral por- 

 tion forms a single oblong ganglion, while the three 

 thoracic ganglia are connected by double longitudi- 

 nal commissures. In most of the other families, the 

 three thoracic ganglia are more or less separated, 

 and the abdominal portion is modilied in various 

 ways. With the Endomj'chidae, Melo'idae and 

 Chrysomelidae, there are only four abdominal 

 ganglia connected by very short double commis- 

 sures ; see Audouin, Ann. d. Sc. Nat. IX. 1826, 

 p. 36, PI. XLII. fig. 16 {Lytta); Brandt, Mediz. 

 Zool. II. p. 103, Taf. XVII. fig. 2, Taf. XIX. fig. 

 19 {Melon and Lytta) ; Newport, Cyclopaed. loc. 

 cit. II. p. 950, fig. 408 {Thaarcha) and Joly, 

 Ann. d. So. Nat. II. 1844, p; 24, PI. IV. fig. 16 

 (fiolaspis). With the Dytisddae, and with Bytu- 

 rua, there are six abdominal ganglia, and the com- 

 missures are also very short ; see Burmeister, 

 Ilandb. loc. cit. Taf. XVI. fig. 9 (Dytiscus). This 

 figure, however, is not fully exact, if compared 

 with that of Blanchard (loc. cit. p. 343, PI. X. tig. 

 1). With the Staphylinidae, Silphidae, and lly- 

 drophilidae, the abdominal portion, altliough com- 

 posed of eight ganglia, is not prolonged much 

 into the abdomen ; it is longe and composed of 

 six to seven ganglia with the Carabidae, Lu- 

 canidae, and Pyrochroidae ; see L. Dufour, 

 Ann. d. Sc. Nat. VIII. 1826, p. 27, PI. XXt. bis, 

 fig. 2 (Carabu-i), and Ibid. XIII. 1840, p. 332, 

 PI. VI. fig. 9 {Pyrochroa). It is even still longer 



and composed of eight ganglia with the Elateridae, 

 Cleridae and Teleplioridae. 



-0 See Blanchard, loc. cit. 



21 AVith those species of the Lamellicornes, and 

 Curculionidae, whose ventral cord is very much 

 concentrated, the eleven large component ganglia 

 are, with the larvae, united into one knotty mass, 

 without any trace of commissuix's ; see Swammer- 

 damm, loc. cit. p. 131, Taf. XXVIII. fig. 1 {Oryc- 

 tes) ; L. Dufour, Ann. d. Sc. Nat. XVIII. 1842, 

 p. 1*0, PI. IV. fig. 11 (Cetonia) ; Burmeister, 

 Zur Naturgesch. d. Calandra, p. 13, fig. 13, 14 ; 

 Blanchard, Ann. d. Sc. Nat. loc. cit. PI. XIV. fig- 

 1 {Calandra}. With the larvae of the Melo'id.ae, 

 Pyrochroidae, Lucanidae, Chrysomelidae, Tene- 

 brionidae, as well as of most of the other famiUes 

 of the Coleoptera, the ventral chain occupies nearly 

 the entire length of the body, and is composed of 

 eleven ganglia having double commissures ; the 

 thoracic ganglia exceed but little in size those of 

 the abdomen ; see Brandt, Mediz. Zool. II. p. 105, 

 Taf. XVII. fig. 20, Taf. XIX. fig. 31 {Meloe and 

 Lytta) ,■ L. Dufour, Ann. d. Sc. Nat. XIU. 1840, 

 p. 327, PI. V. fig. 8 {Pyrochroa), and XVIII. 

 1842, p. 172, PI. V. fig. 17 {Dorcus) ; Newport, 

 Cyclopaed. loc. cit. p. 943, fig. 404 {Timarcha) ; 

 Joly, Ann. d. Sc. Nat. II. 1844, p. 24, PI. IV. fig. 

 14 {Colaspis), and Blanchard, Ibid. PI. XV. fig. 

 7, PI. X. fig. 5 {Chrysomcla and Tenebrio). It 

 is only with the larvae of the Carabidae, Silphidae, 

 Staphylinidae and Diaperidae, that tlie ventral 

 cord, although composed of eight ganglia, does not 

 extend into the last abdominal segments ; while 

 that of the larvae of the Dytiscidae, composed of 

 seven ganglia, does not reach beyond the middle 

 of the abdomen ; see Burmeister, Trans, of the 

 Entomol. Soc. Lond. I. p. 239, PI. .\.\IV. fig. 9 

 {Calosoma) ; Blanchard, Ann. d. Sc. Nat. loc. cit. 

 PI. IX. fig. 3, 5, PI. XI. fig. 4, PI. X. fig. 2 {Sil- 

 pha, Staphylinus, Diaperis, and Dytiscus). 



