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 Lamelli- 

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

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

 to the prothoracic, 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 

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

 body. This is the case with the Cistelidae, Oedenieridae 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 Stomato-gastric nerve arises from the anterior border of the 

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

 of the bi'ain, meet in a ganglion (Ganglion frontale) lying upon the oesoph- 

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

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



18 There has recently appeared a very detailed 

 memoir, accompanied with beautiful figures, on the 

 nervous system of the Coleoptera, by Blancliard ; 

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

 and R^gne animal, illustr. Insectes, PI. III. III. 

 bis. and IV. {Melvlontha, Carabus, Otiorhyn- 

 chus, Cerambyx). . 



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

 1 {Melolontha vulgaris), and Blanchard, loc. cit. 

 An analogous concentration of the nervous system 

 occui-s in the families of Histeridae, Gyrinidae, 

 Nitidulidae, and Scajihididae, where 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 modified in various 

 ways. With the Endomychidae, Meloidae 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 (Meloe and Lytta) ; Newport, Cyclopaed. loc. 

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

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

 (Colaspis). With the Dytiscidae, and with Bytu- 

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

 missures are also very short ; see Bvrmeister, 

 Ilandb. loc. cit. Taf. XVI. fig. 9 i^Dytiscus). This 

 figure, however, is not fully exact, if compared 

 with that of Blancliard (loc. cit. p. 343, PI. X. fig. 

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

 drophilidae, the abdominal portion, although com- 

 posed of eight ganglia, is not prolonged much 

 into the abdomen ; it is longer 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. XXI. bis, 

 fig. 2 (Carabus), 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 Telephoridae. 



'20 See Blanchard, loc. cit. 



21 With 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 commissures ; see Swammer- 

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

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

 p. IW, 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 Melu'idae, 

 Pyrochroidae, Lucanidae, Chrysomelidae, Tene- 

 brionidae, as well as of most of the other families 

 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 {Mcloii and 

 Lytta) ; L. Dufour, Ann. d. Sc. Nat. XIII. 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 (Chrysomela 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 

 Entumol. Soc. Lond. I. p. 239, PI. XXIV. fig. 9 

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

 PI. IX. fig. 3, 5, PI. XI. fig. 4, PI. X. fig. 2 (5i7- 

 pha, Staphylinus, Diaperis, and Dytiscus). 



