INSECTA. 361 



annular or oesophageal nerve, and which constitutes the cephalic 

 roots, or connections of the stomato-gastric system. Each of these 

 nerves passes forwards and divides : the external tract joins one of 

 the maxillary nerves of the sub-cesophageal ganglion ; the internal 

 one converges towards its fellow, and terminates with it in the first 

 of the median cephalic series of ganglions (e), which Lyonnet terms 

 frontal ganglions. The longest nerve in the whole body of the 

 caterpillar is given oflf from these ganglions as it passes along the 

 oesophagus to the stomach and intestines : it was called by Swam- 

 merdara the recurrent nerve. There are two other small ganglions 

 situate in the head of the caterpillar on each side of the large bilobed 

 or cephalic ganglion (a, a). The largest nervous columns connected 

 with the super-oesophageal ganglion, are those which enclose the 

 oesophagus by uniting with the first of the lower series of ganglions (i). 

 From this ganglion nerves are distributed to the mandibles, the max- 

 illas, the lips, and their special organs of sensation or palpi. Two 

 distinct columns connect the first with the second ventral ganglion 

 (2) ; and this is connected by more diverging columns with the 

 third (3). The inter-communicating chords of the remaining ganglions 

 appear single at their anterior part, and bifurcate as they are con- 

 nected with the next ganglion in succession. They are of a greyish 

 blue but transparent colour, and are very elastic. From each side 

 of the abdominal ganglions are given oiFtwo principal branches; the 

 anterior to the muscles chiefly, the posterior chiefly to the integu- 

 ments, but communicating with the muscular branch of the succeed- 

 ing ganglion. From the beginning of the separation of the bifurcated 

 inter-ganglionic columns, or conduits, Lyonnet says, *' there descends 

 a nerve, the extremity of which is enlarged a little above the suc- 

 ceeding ganglion, which sends off" from the enlargement a transverse 

 nerve to the right and to the left, to which I give the name of spinal 

 rein (bride epiniere, o, 0). Of these transverse nerves there are ten 

 pairs ; they terminate chiefly in the stigmata and trachea, but send 

 off" small branches to the skin, and to the dorsal vesseL These are 

 the respiratory ganglia and nerves, and have been erroneously con- 

 sidered as the motor column and nerves. 



The nervous system in perfect insects approaches to its larval con- 

 dition according as the segments of the body and their locomotive 

 appendages are less concentrated and developed ; thus, in the darkling 

 beetle (Melde) the abdominal nervous columns still manifest eight 

 distinct ganglions, of which the last, perhaps including three ganglions 

 of the larva, is now the largest, and radiates its branches to the 

 generative organs. The sub-ocsophageal ganglion sends forward four 

 median branches to the under parts of the mouth, and is connected 



