HIGH SCHOOL ZOOLOGY. 207 



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tures, like the labnim and metastonia of the crayfish, are repre- 

 sented here also, for above the mandibles there is an unpaired 

 labrum articulated to the epicranium by an intermediate chj- 

 jyeus, and projecting into tlie mouth-cavity as the ejnpharynx, 

 while a hypopliarynx is found opposite in the floor of the 

 mouth ; both of these are covei'ed with stiff hairs. 



Although the abdomen has no obvious appendages yet the 

 blades of the ovipositor and the cerci (more conspicuous in the 

 cockroach) q,re, in reality, appendages of the eight, ninth, and 

 tenth segments ; traces of an eleventh segment are also present. 



22. Of very different nature from the appendages, are the 

 wings : these are to be regarded as outgrowths from the notum 

 of the two hinder thoi'acic segments, which have become hinged 

 to the thorax, and penetrated by vascular and respiratory 

 organs. In this genus the anterior wings are less of use in 

 flight than the posterior, and serve partly as wing-covers (elytra). 



23. In the locust, the nervous system is related to the seg- 

 mentation in a way somewhat similar to what we found in the 

 crayfish, bvit it is not so concenti-ated as in the spider. The 

 brain supplies the eyes, ocelli and antennae; the infraceso])haf'eal 

 ganglion, the mouth-parts; the three thoracic segments have each 

 their own ganglion (the last of which supplies the eai-s) ; but 

 there are only five abdominal ganglia situated in the third, 

 fifth, seventh, eighth and ninth segments respectively (Fi^'. 

 141). The intestines have a special ganglion united with the 

 brain by a visceral nerve. 



Little definite is known with regard to the senses of the locust ; 

 the antennse and palps of the jaws have undoubtedly a tactile 

 function, but it is likely that some parts of them may be employed 

 to detect odours and tastes as well. The compound eyes have 

 a similar structure to those of the crayfish, but there are in 

 addition three ocelli (compai-able to a single ommatidium of a 

 compound eye), one of which is situated between the bases of 

 the antennse, the other two, higher up on the front of the head. 



