138 ZOOLOGY. 



plate, as it has an articulated palpus on each side, mncli like those of the 

 former organs. The labium is partly covered by and articulated with the 

 mentuni^ which is articulated to the anterior part of the craniu^n, beneath 

 named the jugulmn. The labial palpi are attached one on each side of the 

 labium near the tongue. The projecting sides of the tongue are named 

 ^ararjloss(B. 



Thorax. The thorax supports the organs of motion, and is attached to the 

 head of an insect by a membranous connexion. Its entire upper and lower 

 surfaces are named respectively tergum and pectum. It is composed of 

 three divisions, named prothorax., mesothorax.^ and inetathorax y the upper 

 surfaces of which are termed pronotum.^ 7nesonotum^ and metanotum., 

 and the inferior surfaces cmtepectus, medipectus, and postpectus.'^ The 

 protliorax bears the anterior pair of feet, but as it bears no wings it is 

 simpler in its structure, and its theoretical parts are more difficult to discover 

 than those of the two other thoracic segments. It is in the latter, therefore, 

 that M'e must look for the subdivisions of these segments. These are 

 generally enumerated from the front backwards, when tlie four subdivisions 

 of the upper part will be the prcBSCutum^ scutwii^ scutellum^ and postscxi- 

 tdluiii^ and those below, \\\q paraptera., sternum., episterna^ and epimera. 

 The term pileura is applied to the sides in descriptions, but it is not limited 

 to any particular part. The sternum is the chief central part with which 

 the two episterna articulate, and the two epimera are near the insertion of 

 the feet, and the paraptera (or tegulm^ oy patagia) near the wings. New- 

 port thinks it exists in a rudimentary condition in the protliorax, but Straus 

 Diirckheim thinks the part referred to by that author is the rudiment of 

 another segment. Tlie mesothoracic scuteljum is often seen wedged 

 between the base of the elytra in the Coleoptera {pjl. 81, figs. 23, 121, 131, 

 &c.) The prothorax and mesothorax have usually each a pair of spiracles, 

 but in the Ilymenoptera the second pair is upon the metathorax. 



The chief appendages of the thorax are the feet, which are never absent. 

 These organs have many modifications to adapt them to their various uses 

 of walking, swimming, grasping, leaping, digging, &c. The thoracic 

 cavities into which the base of the feet is fitted are named acetahitla., and 

 the basal part of the limb which enters them is the coxa j but this is 

 sometimes firmly attached, so as to have no independent motion. Next to 

 the coxa follows a small articulation named the troGhanter j then follows 

 the principal articulation, \X\efemiu\ or thigh, to which succeeds the tibia.^ 

 which is often armed at the end with fixed or movable spines, named 

 calcaria. This part is more generally provided with spines and cilia than 

 the other parts. The tibia is followed by the tarsus, which is made up of 

 several small articulations named ^:>AaZa?i^c5, of which there are never more 

 than five. The end of the tarsi is usually armed with two claws named 

 wig lies. 



* Pro.itclhufi, d'c, •would be more uniform with prothorax, d'c, than antepectns. The name 

 prosternmn cannot be used with propriety, as it is apphed to a minor division (sternum, episterna) 

 of the breast of each thoracic segment. 

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