INSECTA. 363 



action in the Ortliopterous insects. In the Coleoptera, whose elytra 

 do not move in flight, this anastomosis of the nerves does not take 

 place. Four pairs of nerves come into view when the elytral ganglion 

 of the cockroach is exposed from below. The anterior of these runs 

 forward at an acute angle to the muscles of the first and second pairs 

 of legs. The next two anastomose with an alar branch. The third 

 pair enters the second pair of legs, and is distributed to their terminal 

 segments. The posterior nerve passes to the alar plexus. The sub- 

 stance of the bilobed elytral ganglion seems to be superadded to the 

 under or ventral part of the nervous chord. The alar ganglion, formed 

 by a confluence of the fourth and fifth of the larval ganglions, is 

 situated at the same distance from the elytral as this is from the 

 brachial ganglion. It is not quite so broad as the elytral ganglion, 

 the wings which it supplies being shorter than their covers. The 

 anterior nerve enters into communication with the elytral branches, 

 as does also the second nerve, with the addition of branches to the 

 muscles of the legs. The third nerve is distributed to the third 

 pair of legs ; the fourth to the muscles of the wing. The remaining 

 six ganglions of the ventral series are contained in the abdomen : 

 they are smaller than the preceding, the distance between them pro- 

 gressively increasing after the third. The last, formed by the conflu- 

 ence of the eleventh and twelfth ventral ganglions of the larva, is of a 

 triangular form, and the largest of the series. It sends oflF a pair of 

 conspicuous nerves to the cercae or anal antennje. The two inter- 

 ganglionic columns are in contact lengthwise from the head to the 

 anal ganglion. In the Meloe they are smaller, and separated by a 

 marked interspace. The respiratory nerves may be seen on the 

 dorsal aspect above the second, third, and fourth ventral ganglion. 

 If the nervous system of the Blatta be compared with the stages of 

 development of that system in an insect presenting a more con- 

 centrated type in the perfect state, as in the species of butterfly 

 described by Herold*, it will be found to correspond with the sixth 

 stage figured by this author in the pupa of the Papilio brassicce. 



In the predatory leaf-insect {Mantis) the progress of coalescence 

 has reduced the number of abdominal ganglia to four, the three 

 thoracic ganglions continuing distinct, so that the nervous system 

 corresponds with the eighth stage figured by Herold in the Lepidop- 

 terous insect just mentioned. The super-oesophageal mass consists 

 of two triangular lobes having their bases rounded and anterior, and 

 their apex prolonged into the oesophageal chords. Two small nerves 

 are sent off from the anterior part to the ocelli, where they swell into 



* CCXLI. 



