DEFINITION OF AN INSECT. 3 



In these creatures, the different structure of the 

 segments in different parts of the body enables the 

 latter to be divided into three regions as they are 

 called ; one segment forming the head or first region, 

 three going to form the second region or thorax, and 

 nine the third or abdomen. The head is furnished 

 with a pair of jointed organs very variable in length, 

 and often exceedingly curious in their form, which are 

 called the antennae ; and each segment of which the 

 thorax is composed bears a pair of jointed legs. An 

 animal presenting these characters may be safely pro- 

 nounced to be an insect. 



But " to make assurance sure," it may not be amiss 

 to give a slight sketch of the most prominent charac- 

 ters of the groups which have been already alluded to 

 as nearly allied to our little favourites. Not only are 

 these commonly regarded as insects by the unlearned, 

 but the great Linnaeus, the Father of Modern Natural 

 History, included them all in his great class of Insects, 

 which, in fact, represents exactly the group of " arti- 

 culated animals with limbs" (Arthropoda) admitted 

 by all modern zoologists. But although, according 

 to the light which existed in the days of Linnaeus, 

 these creatures might well be placed together in a 

 single class, the researches of his successors soon 

 showed that they presented characters of sufficient 

 importance to justify their being divided into several 

 classes, and in the present day the existence of four 

 such groups is generally admitted. Of these the 

 Insects form one, and the distinctive marks of the 

 other three may be given in few words. 



The nearest approach to the Insects is made by the 

 Myriapoda*, of which the common Centipedes are 

 * Gr. murias, a myriad, and pous, a foot. 



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