INSECTS. 



The Insects, to which we must devote a few pages, afford the first 

 examples of the Articulata— z. e., the jointed animals without vertebrae. 

 Their bodies are composed of a series of rings, and they are separated 

 into at least two, and mostly three, portions, the head being distinct 

 from the body. They pass through a series of changes before attaining 

 the perfect form ; and when they have reached adult age they always 

 possess six jointed legs, neither more nor less, and two antennae, popu- 

 larly called horns or feelers. 



In most instances their preliminary forms, technically called the 

 larva and pupa, are extremely unlike the perfect Insect, but there are 

 some in which, at all events externally, they retain the same shape 

 throughout their entire life. The whole of the growth takes place in 

 the preliminary stages, so that the perfect insect never grows, and the 

 popular idea that a little Insect is necessarily a young one is quite 

 incorrect. 



Insects breathe in a very curious manner. They have no lungs or 

 gills, but their whole body is permeated with a network of tubes, 

 through which the air is conveyed, and by means of which the blood 

 is brought into contact with the vivifying influence of the atmosphere. 

 These breathing-tubes, technically called tracheae, ramify to every 

 portion of the creature and penetrate to the extremities of the limbs, 

 the antennae, and even the wings when those organs exist. Their 

 external orifices are called spiracles, and are set along the sides. 



They have very little internal skeleton, the hard materials which 

 protect the soft vital organs being placed on the exterior, and forming 

 a beautiful coat-of-mail, so constructed as to defend the tender portions 

 within, and yet to permit perfectly free motion on the part of the 

 owner. 



There are many other interesting points in the structure of the 

 Insects, such as the eyes, the wings, the tracheae, etc., which will be 

 described in the course of the following pages. 



The first order is called the Coleoptera — a word of Greek origin, 

 signifying Sheathed-winged Animals — and includes all those insects 

 which are more popularly known under the title of Beetles. In these 

 msects the front pair of wings are modified into stout horny or leathery 

 cases, under which the second pair of wings are folded when not in use. 

 The hmder pair of wings are transparent and membranous in their 

 structure, and when not employed are arranged under the upper pair, 

 technically called the ^ytra, by folds in two directions, one being longi- 

 tudinal and the other transverse. The mouth is furnished with jaws, 

 otten of considerable power, which move horizontally. 



