§szo. 



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.''^^ 



With the Hynienoptera, 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 cord of the 

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

 Tenthredinidae.'i'^' 



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- Bembecidae, with Larra, and Tiplica ; four with 

 nessa urticae and Bombyx mori, see the figures of Tripoxylon, and three with Eucera. 

 Swammerdamm,\oc. cit. p. 387, 230,Taf. XXVIII. 16 The ventral chain of the Tenthredinidae, 

 fig. 3, and Taf. XXXIV. fig. 7 ; also for that of the Apidae, Vespidae and other Hymenoptera, uuder- 

 larva and imago of Cossus lis;niperda, the works of goes, undoubtedly, with the pupae, a metamorpho- 

 Lyonet, Traite, &c., p. 190, PI. IX., and in the sis similar to that occuring with the Lepidoptera. 

 Mem. du Mus. loc. cit. p. 191, PI. LI. (17). For 1' Swammerdamm, loc. cit. p. 108, Taf. XIV. 

 that of Gastropacha pint, pupa and imago, (a pupa of £;)Aemera) ; 3/«rcei rfe Serrcs, Mem. 

 see Suckow, Anat. physiol. Untersuch. p. 40, du Mus. IV. 1818, PI. VIII. (1.) fig. 1 (Jcr/diu/n); 

 T-df. VII. fig. 37, 38 ; but see especially the excel- J. Midler, Nov. Act. Nat. Cur. XIV. Tab. IX. 

 lent description of that of the larva, pupa, and fig. 4, and XII. p. 568, Tab. L. fig. 1 (AcridiuTti 

 imago of Sphinx liffusiri, for which we must and Bacteria); Newport, Cyclop. II. p. 950, fig. 

 thank Newport. PhUos. Trans. 1832, p. 383, PI. 409, 410 (Forjiru/a and Locusta) ; finally, L. Du- 

 XIL XIU.; also, 1834, p. 389, PI. XIII.-XVIII., /our, Ann. d. So. Nat. XIII. 1828, p. 361, PI. 

 and Cyclop. &c. loc. cit. p. 943, fig. 406, 414, 415. XXII. fig. 4 {Forjicula), Recherch. sur les Or- 



14 This metamorphosis of the nervous system thopt. &c. p. 281, PI. 11. fig. 7 (Oedipoda), and p. 

 was first observed by //eroW (Entwickelungsgesch. 561, PI. XI. fig. 160 {Libellula). According to 

 d. Schmetterlinge, loc. cit. Taf II.) with Pontia L. Diifovr, there are seven ventral ganglia with 

 brassicae, and has since been confirmed by New- LibeUiilaand Ephemera, while there are only six 

 port with Sphinx Hf;ustri and Vanessa urticae ; with Per/a and Phrys'anea. But Pictet (Re- 

 see Philos. Trans. 1834, PI. XV. XVI. fig. 20-30, cherch. pour servir a I'hist. et Al'anat. des Phry- 

 and Cyclop, loc. cit. p. 962, fig. 420-423. ganides. PI. II. fig. 33-36) and Burmeister 



15 See Swammerdamm, Bib. der Nat. p. 207, (Ilandb. &c. II. p. 895, 898) assigfi to these In- 

 Taf. XXII. fig. 6 {Aptt Tnellijica) ; Treviranus, secta, ui both their larva and their perfect state, 

 Biologie, V. Taf. I. {Bombuft muscori/m), and eight ventral gangUa. There are even nine of 

 Brandt and Ratzeburg, Medizin. Zool. II. p. 203, these ganglia with the Ephemeridae, according to 

 Taf XXV. fig. 31 {Apia mellijica). For the dis- Burmeister {\oc. c\t. -p. K'i). In the very chub- 

 position of the ventral chain of the Lepidoptera in bed larvae of Myrmeleon there are eight contigu- 

 general, see, moreover, L. Dufour, Recherch. sur ous ventral ganglia beside two thoracic ones (Cit- 

 ies Orthopt., Hymenopt. &c. p. 381. According to ii/er, Lec^ons, &c.. III. p. 341). Loeiv (Germar'K 

 this last-mentioned naturalist, the number of ventral Zeitsch. IV. p. 424) remarks that the proper Neu- 

 ganglia is five with Vespa, Scotia, and with most of roptera are distinguished by the separation of their 

 the Apidae and Andrenidae ; six with OdynerMS, last two abdominal ganglia, while, with all the Or - 

 Sphex, Pompilus, Chrysis, the Ichneumonidae, thoptera, they are fused together.* 



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

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



