^330. 



THE INSECTA. 



411 



■while those of the others are usually fused together. <^''^ During the pupa- 

 state, a remarkable change takes place. The commissures between the 

 first and second, and the third and fourth ganglia, are gradually shortened. 

 The ganglia are thereby gradually approximated, and, in the end, are fused 

 together, forming the two thoracic ganglia of the adult, which send off 

 nerves to the legs, and to the muscles of the wings. At the same time, the 

 fifth and sixth ganglia entirely disappear or are fused into one.^'^' 



AVith the Hymenoptera, the ventral cord is composed of seven to eight 

 ganglia connected by double commissures. The first of these, smaller 

 than the second, is, like it, produced by the fusion of several ganglia ; and 

 both are situated in the thorax. Of the remaining five or six abdominal 

 ganglia, the last two are closely approximated, or fused into one.*''"^ Here, 

 as with the Lepidoptera, the number of ganglia in the ventral coi-d of the 

 larvae, is eleven, as has been specially shown in the false caterpillars of the 

 Tenthredinidae. '"^' 



With the Orthoptera, and Neuroptera, the nervous system is nearly 

 always composed, in their various states, of three thoracic and six to seven 

 abdominal ganglia connected by double commissures and forming a chain 

 as long as the body.'^'' 



With the Coleoptera, the number and disposition of the ventral ganglia 

 present the widest variations of all. The longitudinal commissures, always 

 double, are shortened or even wholly wanting at certain points. The 

 ganglionic chain is, therefore, more or less abbreviated, and sometimes the 

 ganglia are almost fused into a single mass. In this respect this system 

 here presents two principal types, the limits between which, however, have 



13 For the nervous system of the larvae of Va- 

 nessa urticae and Bombyx n)ori, see the fisrures of 

 Swainmerdamm ^\oc. cit. p. 387, '230,Taf. XXVIII. 

 fif?. 3, and Taf. XXXIV. fig. 7 ; also for that of the 

 larva and imago of Cossus /i^niperda, the works of 

 Lyonet, Tralfe, &c., p. 19(j, PI. IX., and in the 

 Mem. du Mus. loc. cit. p. 191, PI. LI. (17). For 

 that of Gastropacha pint, pupa and imago, 

 see Suckoiv, Anat. physiol. Untersuch, p. 40, 

 Taf. VII. fig. 37, 38 ; but see especially the excel- 

 lent description of tliat of the larva, pupa, and 

 imago of Sphinx lisustri, for which we must 

 tliank Newport. Philos. Trans. 1832, p. 383, PI. 

 XII. XIII.; also, 1834, p. 389, PI. XIII.-XVIII., 

 and Cyclop. &c. loc. cit. p. 943, fig. 406, 414, 415. 



1-t This metamorphosis of the nervous system 

 was first observed by Herold (Entwickelungsgesch. 

 d. Schmetterlinge, loc. cit. Taf. II.) with Pontia 

 brassicae, and has smce been confirmed by New- 

 port with Sphinx li^ustri and Vanessa urticae ; 

 see Philos. Trans. 1834, PI. XV.. XVI. fig. 20-30, 

 and pyclop. loc. cit. p. 962, fig. 420-423. 



15 See Swammerdamm, Bib. der Nat. p. 207, 

 Taf. XXII. fig. 6 (A])is meUißca) ; Treviranus, 

 Biologie, V. Taf. I. (Bambus muscorum), and 

 Brandt and Ratzeburg, Medizin. Zool. II. p. 203, 

 Taf. XXV. fig. 31 (Apis mellißca). For the dis- 

 position of the ventral chain of the Lepidoptera in 

 general, see, moreover, L. Dufour, Recherch. sur 

 les Orthopt., Hymenopt. &c. p. 381. According to 

 this last-mentioned naturalist, the number of ventral 

 ganglia is five with Vespa, Scolia, and with most of 

 the Apidae and Andreuidae ; six with Odynerus, 

 Sphex, Pompilus, Chrysis, the I:hneiimomdae, 



Bembecidae, with Larra, and Tiplica ; four with 

 Tripoxylon, and three with Eucera. 



16 The ventral chain of the Tenthredinidae, 

 Apidae, Vespidae and other Hymenoptera, under- 

 goes, undoubtedly, with the pupae, a metamorjjho 

 sis similar to that occuring witii the Lepidoptera. 



li" Swammerdamm , loc. cit. p. 108, Taf. XIV. 

 (a pupa of Ephemera) ; Marcel de Serres, Mem. 

 du Mus. IV. 1818, PI. VIII. (1.) fig. 1 (Acridium); 

 J. Mxlller, Nov. Act. Nat. Cur. XIV. Tab. IX. 

 fig. 4, and XII. p. 568, Tab. L. fig. 1 (Acridium 

 and Bacteria) ; Newport, Cyclop. II. p. 950, fig. 

 409, 410 (Forßcula and Lociista) ; finally, L. Du- 

 four, Ann. d. Sc. Nat. XIII. 1828, p. 361, PI. 

 XXII. fig. 4 {Forßcula')., Recherch. sur les Or- 

 thopt. &c. p. 281, PI. II. fig. 7 (Oedipoda), and p. 

 561, PI. XI. fig. 160 (Libellula). According to 

 L. Dufour, there are seven ventral ganglia with 

 Libellula a.nd Ephemera, while there are only six 

 with Perla and Phrysranea. But Pictet (Re- 

 cherch. pour servir i I'hist. et Al'anat. des Phry- 

 ganides. PI. II. fig. 33-36) and Burmeister 

 (Handb. &c. II. p. 895, 898) assign to these In- 

 secta, in both theii- larva and their perfect state, 

 eight ventral ganglia. There are even nine of 

 these ganglia with the Ephemeridae, according to 

 Burmeister (loc. cit. p. 763). In the very chub- 

 bed larvae of Myr/neleon there are eight contigu- 

 ous ventral ganglia beside two thoracic ones (Cu- 

 vier, Lepons, &c.. III. p. 341). Loeiv (Germar^s 

 Zeitsch. IV. p. 424) remarks that the proper Neu- 

 roptera are distinguished by the separation of their 

 last two abdominal ganglia, while, with all the Or- 

 thoptera, they are fused together.* 



* [ § 330, note 17.] See also for a description femoratum, Leidy, Proceed. Acad. Sc. Philad. 

 and figures of the nervous system of Spectrum 1846, III. p. 83. — Ed. 



