320 



ZOOLOGY. 



maxillge, and labium. The mandibular nerves project for- 

 ward and arise from the anterior part of the ganglion, near 

 the origin of the supra-cesophageal commissures, while the 

 maxillary and labial nerves are directed downward into 

 those organs. 



The sympathetic ganglia are three in number ; one situ- 

 ated just behind the supra-cesophageal ganglion (Fig. 273, 

 as), resting on the oesophagus, and two others situated each 



side of the crop, low down. Each of 

 the two posterior ganglia is supplied 

 by a nerve from the anterior ganglion. 

 Two nerves pass under the crop con- 

 necting the posterior ganglia, and 

 from each posterior ganglion a nerve 

 is sent backward to the end of the 

 proventriculus. A pair of nerves pass 

 under the oesophagus from each side 

 of the anterior sympathetic ganglion, 

 and another pair pass downward to a 

 round white body, whose nature is 

 unknown (Fig. 273, u}. 



Fig. 280 represents an enlarged 

 view of the brain and sympathetic 

 nerve of a moth. The heart is a long 

 tube lying in the abdomen, dilating 

 at six places along its course, and 

 ending in a conical point near the 

 end of the abdomen ; it is held in 

 place by fine muscular bands. 



All insects breathe by means of a 

 complicated system of air-tubes rami- 

 fying throughout the body, the air 

 entering through a row of spiracles, or air-holes, or breath- 

 ing-holes (stigmata), in the sides of the body. There are in 

 locusts two pairs of thoracic and eight pairs of abdominal 

 spiracles. The first thoracic pair (Fig. 281) is situated on 

 the membrane connecting the prothorax and mesothorax, 

 and is covered by the hinder edge of the protergum (usually 

 called prothorax). The second spiracle is situated on the 



Fig. 280. Supra-cesopha- 

 geal ganglion and visceral (or 

 sympathetic) nervous system 

 of the silk-worm moth(Bw/i- 

 b>/x moii). gs, Supra-oei-so- 

 phageal ganglion ('' brain ") ; 

 a, antennary nerve ; 0, optic 

 nerve ; r, azygos trunk of the 

 visceral nervous system ; r', 

 its roots arising from the 

 Bupra-ecsophageal ganglion ; 

 , paired nerve with its gangli- 

 onic enlargements s' s". 

 After Brandt, from Gegen- 

 baur. 



