. A manual of zoology for the use of students : with a general introduction on the principles of zoology . Zoology. ANNULOSA: INSECTA. 249 more or less hardened ,by the deposition of chitine, and usually forms a resisting exoskeleton, to which the muscles are attached. The segments of the head are amalgamated into a single piece, â which, bears a pair of jointed feelers or antennae, a pair of eyes, usually compound, and the appendages of the mouth. The segments of the thorax are also amalgamated into a single piece; but this, nevertheless, admits of separation into its con- stituent three somi
. A manual of zoology for the use of students : with a general introduction on the principles of zoology . Zoology. ANNULOSA: INSECTA. 249 more or less hardened ,by the deposition of chitine, and usually forms a resisting exoskeleton, to which the muscles are attached. The segments of the head are amalgamated into a single piece, â which, bears a pair of jointed feelers or antennae, a pair of eyes, usually compound, and the appendages of the mouth. The segments of the thorax are also amalgamated into a single piece; but this, nevertheless, admits of separation into its con- stituent three somites (fig. 83). These are termed respect- ively, from before backwards, the "prothorax," "mesothorax," and " metathorax," and each bears a pair of jointed legs. In the great majority of Insects, the dorsal arches of the mesotho- rax and metathorax give origin each to a pair of wings. Each leg consists of from six to nine joints. The first of these, which is at- tached to the sternal sur- face of the thorax, is called the "coxa," and is suc- ceeded by a short joint termed the "; The trochanter is followed by a joipt, often of large size, called the "femur," and this has articulated to it the " tarsus," which may be composed of from two to five joints. The wings of Insects are membranous "flatten- ed vesicles, sustained by slender but firm hollow tubes, called ' nervures,' along which branches of the tracheae and channels of the circulation are con- ; â (Owen.) Ac- cording to Newport, the. Fig. 83.âDi^gl^am of Insect, a Head, carrj'ing the eyes and antennae; ^Prothorax, carrying the first pair of legs; rMesothorax^ carrj'ing the second pair of legs and first pair of wings; a Metathorax, with the third pair of legs and the second ^air of wings; e Abdomen, without limbs, but haym^ terminal appendages subservient to reproduction. wings of Insects are "expanded portions of the com
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Keywords: ., bookauthorni, bookcentury1800, bookdecade1870, booksubjectzoology
