66 



All of these animals agree in having the body composed of more o 

 less distinct rings or segments, and in having limbs composed of sev 

 eral pieces connected by movable joints; in other words they are al 

 articulated animals, belonging to 'that grand division of the anima 

 kingdom called Mrticulata. 



Having made these examinations we can easily understand thi 

 characters by which we define or designate an insect which are a 

 follows : 



• Insects are those articulated animals which have the body divided into thre 

 sections, the head, thorax and abdomen ; the head distinct and bearing on 

 pair of atfennse, six articulated legs attached to the thorax; wings, when pres 

 ent, attached to the thorax. 



Other characters relating to the digestive and respiratory organs 

 and nervous system might be given, but these have already beer 

 given by Dr. Le Baron, and the above characters are sufficient for oui 

 present purposes. 



Taking this definition as our guide, we find that beetles, cock 

 roaches, crickets, grasshoppers, chinch-bugs, squash-bugs, dragon-flies 

 bees, wasps, ants, butterflies, moths, house-flies and mosquitoes, are 

 all insects, but that spiders, ticks, millipeds, centipedes and manv 

 other small animals often called insects, are, in fact, not true insects. 



The sub-kingdom, or grand division of the animal kingdom, called 

 Articulata, and to which all the animals we have mentioned belong, is 

 divided into groups or divisions, each called a Class, all the true Insects 

 taken together forming one Class, the millipeds, centipedes, and ani- 

 mals of thftt kind forming another Class, the spiders, ticks, and 

 animals of that kind forming another Class, etc. 



We have defined, an Insect as an articulate animal with just six 

 legs; yet there are caterpillars with more than twice this number, 

 and these change into butterflies, which are true insects. 



In giving the characters which define the Class, order or species of 

 insects, we usually select the perfect or complete form. Therefore, in 

 attempting to determine or describe a species it is necessary to know 

 in what stage .of its existence the specimen is. as the characters 

 given, unless otherwise expresslv stated, always apply to the perfect 

 or complete state. Take, for example the caterpilWand the butter- 

 fly ; the one a loathsome worm, divided by cross indentations into 

 similar rings, possessing numerous legs differing in character, with 

 biting jaws, and wingless, the other with a body very different in> 

 form, possessing four wings, only six legs which are slender and 

 101 nted ; and the mouth now a long flexible tube. As every reader 

 knows, the gay butterfly was once a caterpiller ; in other words, that 

 these widely different forms are but the different stages of the same 

 insect As is equally well known, the caterpillar was once closed, 

 around by the walls of a tiny egg; and t»at before it can change its 

 somber dress for the bright colorsof the butterfly, it must pass through 

 another stage where it must rest quite for a time as a chrysalis. It is I 

 evident, therefore, that there are four stages in the life of an insect; firsjt I 

 the egg stare, second the caterpillar or larva state, third the crysalis or J 

 pupa state, and fourth the complete and perfect state to which the 

 term imago is frequently applied. 



